diff --git a/NEWS.md b/NEWS.md
index 121a07446baeb..ab4abedd3a3f3 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -127,6 +127,10 @@ Deprecated or removed
     Ternaries must now include some amount of whitespace, e.g. `x ? a : b` rather than
     `x? a : b` ([#22523]).
 
+  * The operating system identification functions: `is_linux`, `is_bsd`, `is_apple`, `is_unix`,
+    and `is_windows`, have been deprecated in favor of `Sys.islinux`, `Sys.isbsd`, `Sys.isapple`,
+    `Sys.isunix`, and `Sys.iswindows`, respectively ([#22182]).
+
 
 Julia v0.6.0 Release Notes
 ==========================
@@ -920,6 +924,7 @@ Command-line option changes
 [#22038]: https://github.com/JuliaLang/julia/issues/22038
 [#22062]: https://github.com/JuliaLang/julia/issues/22062
 [#22064]: https://github.com/JuliaLang/julia/issues/22064
+[#22182]: https://github.com/JuliaLang/julia/issues/22182
 [#22187]: https://github.com/JuliaLang/julia/issues/22187
 [#22188]: https://github.com/JuliaLang/julia/issues/22188
 [#22224]: https://github.com/JuliaLang/julia/issues/22224
diff --git a/base/c.jl b/base/c.jl
index 3385e18b4e9d2..9360dc21f202a 100644
--- a/base/c.jl
+++ b/base/c.jl
@@ -18,7 +18,8 @@ Equivalent to the native `char` c-type.
 """
 Cchar
 
-if is_windows()
+# The ccall is equivalent to Sys.iswindows(), but that's not defined yet
+if ccall(:jl_get_UNAME, Any, ()) === :NT
     const Clong = Int32
     const Culong = UInt32
     const Cwchar_t = UInt16
@@ -49,7 +50,7 @@ Equivalent to the native `wchar_t` c-type ([`Int32`](@ref)).
 """
 Cwchar_t
 
-if !is_windows()
+if ccall(:jl_get_UNAME, Any, ()) !== :NT
     const sizeof_mode_t = ccall(:jl_sizeof_mode_t, Cint, ())
     if sizeof_mode_t == 2
         const Cmode_t = Int16
@@ -118,7 +119,7 @@ end
 # symbols are guaranteed not to contain embedded NUL
 convert(::Type{Cstring}, s::Symbol) = Cstring(unsafe_convert(Ptr{Cchar}, s))
 
-if is_windows()
+if ccall(:jl_get_UNAME, Any, ()) === :NT
 """
     Base.cwstring(s)
 
diff --git a/base/client.jl b/base/client.jl
index 4013fcd42ceb1..02afb2fe3199f 100644
--- a/base/client.jl
+++ b/base/client.jl
@@ -102,7 +102,7 @@ function repl_cmd(cmd, out)
                 end
                 cd(ENV["OLDPWD"])
             else
-                cd(@static is_windows() ? dir : readchomp(`$shell -c "echo $(shell_escape(dir))"`))
+                cd(@static Sys.iswindows() ? dir : readchomp(`$shell -c "echo $(shell_escape(dir))"`))
             end
         else
             cd()
@@ -110,7 +110,7 @@ function repl_cmd(cmd, out)
         ENV["OLDPWD"] = new_oldpwd
         println(out, pwd())
     else
-        run(ignorestatus(@static is_windows() ? cmd : (isa(STDIN, TTY) ? `$shell -i -c "$(shell_wrap_true(shell_name, cmd))"` : `$shell -c "$(shell_wrap_true(shell_name, cmd))"`)))
+        run(ignorestatus(@static Sys.iswindows() ? cmd : (isa(STDIN, TTY) ? `$shell -i -c "$(shell_wrap_true(shell_name, cmd))"` : `$shell -c "$(shell_wrap_true(shell_name, cmd))"`)))
     end
     nothing
 end
@@ -385,7 +385,7 @@ function _start()
                 global is_interactive |= !isa(STDIN, Union{File, IOStream})
                 color_set || (global have_color = false)
             else
-                term = Terminals.TTYTerminal(get(ENV, "TERM", @static is_windows() ? "" : "dumb"), STDIN, STDOUT, STDERR)
+                term = Terminals.TTYTerminal(get(ENV, "TERM", @static Sys.iswindows() ? "" : "dumb"), STDIN, STDOUT, STDERR)
                 global is_interactive = true
                 color_set || (global have_color = Terminals.hascolor(term))
                 quiet || REPL.banner(term,term)
diff --git a/base/dSFMT.jl b/base/dSFMT.jl
index bd22f22a2fa39..919bfc2e7e01e 100644
--- a/base/dSFMT.jl
+++ b/base/dSFMT.jl
@@ -163,7 +163,7 @@ end
 
 ## Windows entropy
 
-if is_windows()
+if Sys.iswindows()
     function win32_SystemFunction036!(a::Array)
         ccall((:SystemFunction036, :Advapi32), stdcall, UInt8, (Ptr{Void}, UInt32), a, sizeof(a))
     end
diff --git a/base/datafmt.jl b/base/datafmt.jl
index e3d8867a4b649..4be76210719b4 100644
--- a/base/datafmt.jl
+++ b/base/datafmt.jl
@@ -120,7 +120,7 @@ readdlm_auto(input::IO, dlm::Char, T::Type, eol::Char, auto::Bool; opts...) =
     readdlm_string(readstring(input), dlm, T, eol, auto, val_opts(opts))
 function readdlm_auto(input::AbstractString, dlm::Char, T::Type, eol::Char, auto::Bool; opts...)
     optsd = val_opts(opts)
-    use_mmap = get(optsd, :use_mmap, is_windows() ? false : true)
+    use_mmap = get(optsd, :use_mmap, Sys.iswindows() ? false : true)
     fsz = filesize(input)
     if use_mmap && fsz > 0 && fsz < typemax(Int)
         a = open(input, "r") do f
diff --git a/base/deprecated.jl b/base/deprecated.jl
index 828b3ce5c7538..7fd872091052e 100644
--- a/base/deprecated.jl
+++ b/base/deprecated.jl
@@ -1503,6 +1503,13 @@ function bkfact!(A::StridedMatrix, uplo::Symbol, symmetric::Bool = issymmetric(A
     return bkfact!(symmetric ? Symmetric(A, uplo) : Hermitian(A, uplo), rook)
 end
 
+# PR #22182
+@deprecate is_apple   Sys.isapple
+@deprecate is_bsd     Sys.isbsd
+@deprecate is_linux   Sys.islinux
+@deprecate is_unix    Sys.isunix
+@deprecate is_windows Sys.iswindows
+
 # END 0.7 deprecations
 
 # BEGIN 1.0 deprecations
diff --git a/base/distributed/cluster.jl b/base/distributed/cluster.jl
index 3fdb113989573..cae3f8ffec4d5 100644
--- a/base/distributed/cluster.jl
+++ b/base/distributed/cluster.jl
@@ -960,7 +960,7 @@ end
 function disable_nagle(sock)
     # disable nagle on all OSes
     ccall(:uv_tcp_nodelay, Cint, (Ptr{Void}, Cint), sock.handle, 1)
-    @static if is_linux()
+    @static if Sys.islinux()
         # tcp_quickack is a linux only option
         if ccall(:jl_tcp_quickack, Cint, (Ptr{Void}, Cint), sock.handle, 1) < 0
             warn_once("Networking unoptimized ( Error enabling TCP_QUICKACK : ", Libc.strerror(Libc.errno()), " )")
diff --git a/base/distributed/managers.jl b/base/distributed/managers.jl
index d32da4d90c765..6989420822720 100644
--- a/base/distributed/managers.jl
+++ b/base/distributed/managers.jl
@@ -459,7 +459,7 @@ function socket_reuse_port()
         s = TCPSocket(delay = false)
 
         # Some systems (e.g. Linux) require the port to be bound before setting REUSEPORT
-        bind_early = is_linux()
+        bind_early = Sys.islinux()
 
         bind_early && bind_client_port(s)
         rc = ccall(:jl_tcp_reuseport, Int32, (Ptr{Void},), s.handle)
diff --git a/base/env.jl b/base/env.jl
index 254f8633f6eef..c6010c193cc6d 100644
--- a/base/env.jl
+++ b/base/env.jl
@@ -1,6 +1,6 @@
 # This file is a part of Julia. License is MIT: https://julialang.org/license
 
-if is_windows()
+if Sys.iswindows()
     const ERROR_ENVVAR_NOT_FOUND = UInt32(203)
 
     _getenvlen(var::Vector{UInt16}) = ccall(:GetEnvironmentVariableW,stdcall,UInt32,(Ptr{UInt16},Ptr{UInt16},UInt32),var,C_NULL,0)
@@ -84,7 +84,7 @@ delete!(::EnvHash, k::AbstractString) = (_unsetenv(k); ENV)
 setindex!(::EnvHash, v, k::AbstractString) = _setenv(k,string(v))
 push!(::EnvHash, k::AbstractString, v) = setindex!(ENV, v, k)
 
-if is_windows()
+if Sys.iswindows()
     start(hash::EnvHash) = (pos = ccall(:GetEnvironmentStringsW,stdcall,Ptr{UInt16},()); (pos,pos))
     function done(hash::EnvHash, block::Tuple{Ptr{UInt16},Ptr{UInt16}})
         if unsafe_load(block[1]) == 0
diff --git a/base/event.jl b/base/event.jl
index ed701f3148516..280f8c3b9e219 100644
--- a/base/event.jl
+++ b/base/event.jl
@@ -247,7 +247,7 @@ function wait()
     # unreachable
 end
 
-if is_windows()
+if Sys.iswindows()
     pause() = ccall(:Sleep, stdcall, Void, (UInt32,), 0xffffffff)
 else
     pause() = ccall(:pause, Void, ())
diff --git a/base/exports.jl b/base/exports.jl
index 34e266a0ee002..bc0cb63d6ea47 100644
--- a/base/exports.jl
+++ b/base/exports.jl
@@ -1257,14 +1257,6 @@ export
     @code_llvm,
     @code_native,
 
-    # platform-conditional code
-    @static,
-    is_windows,
-    is_linux,
-    is_apple,
-    is_bsd,
-    is_unix,
-
     # tasks
     @schedule,
     @sync,
@@ -1294,6 +1286,7 @@ export
     @goto,
     @view,
     @views,
+    @static,
 
 # SparseArrays module re-exports
     SparseArrays,
diff --git a/base/file.jl b/base/file.jl
index b9e85066eaaaa..9876aeb5ac89a 100644
--- a/base/file.jl
+++ b/base/file.jl
@@ -51,7 +51,7 @@ function cd(dir::AbstractString)
 end
 cd() = cd(homedir())
 
-if is_windows()
+if Sys.iswindows()
     function cd(f::Function, dir::AbstractString)
         old = pwd()
         try
@@ -91,7 +91,7 @@ this function throws an error. See [`mkpath`](@ref) for a function which creates
 required intermediate directories.
 """
 function mkdir(path::AbstractString, mode::Unsigned=0o777)
-    @static if is_windows()
+    @static if Sys.iswindows()
         ret = ccall(:_wmkdir, Int32, (Cwstring,), path)
     else
         ret = ccall(:mkdir, Int32, (Cstring, UInt32), path, mode)
@@ -136,7 +136,7 @@ directory, then all contents are removed recursively.
 function rm(path::AbstractString; force::Bool=false, recursive::Bool=false)
     if islink(path) || !isdir(path)
         try
-            @static if is_windows()
+            @static if Sys.iswindows()
                 # is writable on windows actually means "is deletable"
                 if (filemode(path) & 0o222) == 0
                     chmod(path, 0o777)
@@ -155,7 +155,7 @@ function rm(path::AbstractString; force::Bool=false, recursive::Bool=false)
                 rm(joinpath(path, p), force=force, recursive=true)
             end
         end
-        @static if is_windows()
+        @static if Sys.iswindows()
             ret = ccall(:_wrmdir, Int32, (Cwstring,), path)
         else
             ret = ccall(:rmdir, Int32, (Cstring,), path)
@@ -254,7 +254,7 @@ function touch(path::AbstractString)
     end
 end
 
-if is_windows()
+if Sys.iswindows()
 
 function tempdir()
     temppath = Vector{UInt16}(32767)
@@ -536,7 +536,7 @@ function sendfile(src::AbstractString, dst::AbstractString)
     end
 end
 
-if is_windows()
+if Sys.iswindows()
     const UV_FS_SYMLINK_JUNCTION = 0x0002
 end
 
@@ -550,20 +550,20 @@ Creates a symbolic link to `target` with the name `link`.
     soft symbolic links, such as Windows XP.
 """
 function symlink(p::AbstractString, np::AbstractString)
-    @static if is_windows()
+    @static if Sys.iswindows()
         if Sys.windows_version() < Sys.WINDOWS_VISTA_VER
             error("Windows XP does not support soft symlinks")
         end
     end
     flags = 0
-    @static if is_windows()
+    @static if Sys.iswindows()
         if isdir(p)
             flags |= UV_FS_SYMLINK_JUNCTION
             p = abspath(p)
         end
     end
     err = ccall(:jl_fs_symlink, Int32, (Cstring, Cstring, Cint), p, np, flags)
-    @static if is_windows()
+    @static if Sys.iswindows()
         if err < 0 && !isdir(p)
             Base.warn_once("Note: on Windows, creating file symlinks requires Administrator privileges.")
         end
diff --git a/base/filesystem.jl b/base/filesystem.jl
index 0a04e0f3e98f9..48e136d86f924 100644
--- a/base/filesystem.jl
+++ b/base/filesystem.jl
@@ -44,7 +44,7 @@ import Base:
     skip, stat, unsafe_read, unsafe_write, transcode, uv_error, uvhandle,
     uvtype, write
 
-if is_windows()
+if Sys.iswindows()
     import Base: cwstring
 end
 
diff --git a/base/initdefs.jl b/base/initdefs.jl
index 4535a718a5fd7..fd890e8a5da77 100644
--- a/base/initdefs.jl
+++ b/base/initdefs.jl
@@ -50,7 +50,7 @@ const LOAD_CACHE_PATH = String[]
 function init_load_path()
     vers = "v$(VERSION.major).$(VERSION.minor)"
     if haskey(ENV, "JULIA_LOAD_PATH")
-        prepend!(LOAD_PATH, split(ENV["JULIA_LOAD_PATH"], @static is_windows() ? ';' : ':'))
+        prepend!(LOAD_PATH, split(ENV["JULIA_LOAD_PATH"], @static Sys.iswindows() ? ';' : ':'))
     end
     push!(LOAD_PATH, abspath(JULIA_HOME, "..", "local", "share", "julia", "site", vers))
     push!(LOAD_PATH, abspath(JULIA_HOME, "..", "share", "julia", "site", vers))
diff --git a/base/interactiveutil.jl b/base/interactiveutil.jl
index 32cfb81047023..f08e1d65456a4 100644
--- a/base/interactiveutil.jl
+++ b/base/interactiveutil.jl
@@ -10,7 +10,7 @@ for use within backticks. You can change the editor by setting `JULIA_EDITOR`, `
 `EDITOR` as an environment variable.
 """
 function editor()
-    if is_windows() || is_apple()
+    if Sys.iswindows() || Sys.isapple()
         default_editor = "open"
     elseif isfile("/etc/alternatives/editor")
         default_editor = "/etc/alternatives/editor"
@@ -49,11 +49,11 @@ function edit(path::AbstractString, line::Integer=0)
         cmd = line != 0 ? `$command $path -l $line` : `$command $path`
     elseif startswith(name, "subl") || startswith(name, "atom")
         cmd = line != 0 ? `$command $path:$line` : `$command $path`
-    elseif name == "code" || (is_windows() && uppercase(name) == "CODE.EXE")
+    elseif name == "code" || (Sys.iswindows() && uppercase(name) == "CODE.EXE")
         cmd = line != 0 ? `$command -g $path:$line` : `$command -g $path`
     elseif startswith(name, "notepad++")
         cmd = line != 0 ? `$command $path -n$line` : `$command $path`
-    elseif is_apple() && name == "open"
+    elseif Sys.isapple() && name == "open"
         cmd = `open -t $path`
         line_unsupported = true
     else
@@ -62,8 +62,8 @@ function edit(path::AbstractString, line::Integer=0)
         line_unsupported = true
     end
 
-    if is_windows() && name == "open"
-        @static is_windows() && # don't emit this ccall on other platforms
+    if Sys.iswindows() && name == "open"
+        @static Sys.iswindows() && # don't emit this ccall on other platforms
             systemerror(:edit, ccall((:ShellExecuteW, "shell32"), stdcall, Int,
                                      (Ptr{Void}, Cwstring, Cwstring, Ptr{Void}, Ptr{Void}, Cint),
                                      C_NULL, "open", path, C_NULL, C_NULL, 10) ≤ 32)
@@ -90,7 +90,7 @@ edit(file, line::Integer) = error("could not find source file for function")
 
 # terminal pager
 
-if is_windows()
+if Sys.iswindows()
     function less(file::AbstractString, line::Integer)
         pager = get(ENV, "PAGER", "more")
         g = pager == "more" ? "" : "g"
@@ -123,7 +123,7 @@ less(file, line::Integer) = error("could not find source file for function")
 
 # clipboard copy and paste
 
-if is_apple()
+if Sys.isapple()
     function clipboard(x)
         open(pipeline(`pbcopy`, stderr=STDERR), "w") do io
             print(io, x)
@@ -131,7 +131,7 @@ if is_apple()
     end
     clipboard() = readstring(`pbpaste`)
 
-elseif is_linux()
+elseif Sys.islinux()
     _clipboardcmd = nothing
     function clipboardcmd()
         global _clipboardcmd
@@ -158,7 +158,7 @@ elseif is_linux()
         readstring(pipeline(cmd, stderr=STDERR))
     end
 
-elseif is_windows()
+elseif Sys.iswindows()
     # TODO: these functions leak memory and memory locks if they throw an error
     function clipboard(x::AbstractString)
         if containsnul(x)
@@ -262,21 +262,21 @@ function versioninfo(io::IO=STDOUT; verbose::Bool=false, packages::Bool=false)
         println(io, "DEBUG build")
     end
     println(io, "Platform Info:")
-    println(io, "  OS: ", is_windows() ? "Windows" : is_apple() ?
+    println(io, "  OS: ", Sys.iswindows() ? "Windows" : Sys.isapple() ?
         "macOS" : Sys.KERNEL, " (", Sys.MACHINE, ")")
 
     if verbose
         lsb = ""
-        if is_linux()
+        if Sys.islinux()
             try lsb = readchomp(pipeline(`lsb_release -ds`, stderr=DevNull)) end
         end
-        if is_windows()
+        if Sys.iswindows()
             try lsb = strip(readstring(`$(ENV["COMSPEC"]) /c ver`)) end
         end
         if !isempty(lsb)
             println(io, "      ", lsb)
         end
-        if is_unix()
+        if Sys.isunix()
             println(io, "  uname: ", readchomp(`uname -mprsv`))
         end
     end
@@ -592,7 +592,7 @@ end
 # file downloading
 
 downloadcmd = nothing
-if is_windows()
+if Sys.iswindows()
     function download(url::AbstractString, filename::AbstractString)
         res = ccall((:URLDownloadToFileW,:urlmon),stdcall,Cuint,
                     (Ptr{Void},Cwstring,Cwstring,Cuint,Ptr{Void}),C_NULL,url,filename,0,C_NULL)
diff --git a/base/libc.jl b/base/libc.jl
index 3eae38c4e54e5..fe3f46d446f9c 100644
--- a/base/libc.jl
+++ b/base/libc.jl
@@ -6,7 +6,7 @@ import Base: transcode
 
 export FILE, TmStruct, strftime, strptime, getpid, gethostname, free, malloc, calloc, realloc,
     errno, strerror, flush_cstdio, systemsleep, time, transcode
-if is_windows()
+if Sys.iswindows()
     export GetLastError, FormatMessage
 end
 
@@ -23,13 +23,13 @@ end
 
 Base.cconvert(::Type{Int32}, fd::RawFD) = fd.fd
 
-dup(x::RawFD) = RawFD(ccall((@static is_windows() ? :_dup : :dup), Int32, (Int32,), x.fd))
+dup(x::RawFD) = RawFD(ccall((@static Sys.iswindows() ? :_dup : :dup), Int32, (Int32,), x.fd))
 dup(src::RawFD, target::RawFD) = systemerror("dup", -1 ==
-    ccall((@static is_windows() ? :_dup2 : :dup2), Int32,
+    ccall((@static Sys.iswindows() ? :_dup2 : :dup2), Int32,
                 (Int32, Int32), src.fd, target.fd))
 
 # Wrapper for an OS file descriptor (for Windows)
-if is_windows()
+if Sys.iswindows()
     struct WindowsRawSocket
         handle::Ptr{Void}   # On Windows file descriptors are HANDLE's and 64-bit on 64-bit Windows
     end
@@ -67,7 +67,7 @@ modestr(s::IO) = modestr(isreadable(s), iswritable(s))
 modestr(r::Bool, w::Bool) = r ? (w ? "r+" : "r") : (w ? "w" : throw(ArgumentError("neither readable nor writable")))
 
 function FILE(fd::RawFD, mode)
-    FILEp = ccall((@static is_windows() ? :_fdopen : :fdopen), Ptr{Void}, (Cint, Cstring), fd, mode)
+    FILEp = ccall((@static Sys.iswindows() ? :_fdopen : :fdopen), Ptr{Void}, (Cint, Cstring), fd, mode)
     systemerror("fdopen", FILEp == C_NULL)
     FILE(FILEp)
 end
@@ -102,9 +102,9 @@ flush_cstdio() = ccall(:jl_flush_cstdio, Void, ())
 ## time-related functions ##
 
 # TODO: check for usleep errors?
-if is_unix()
+if Sys.isunix()
     systemsleep(s::Real) = ccall(:usleep, Int32, (UInt32,), round(UInt32, s*1e6))
-elseif is_windows()
+elseif Sys.iswindows()
     function systemsleep(s::Real)
         ccall(:Sleep, stdcall, Void, (UInt32,), round(UInt32, s * 1e3))
         return Int32(0)
@@ -202,7 +202,7 @@ function strptime(fmt::AbstractString, timestr::AbstractString)
         # TODO: better error message
         throw(ArgumentError("invalid arguments"))
     end
-    @static if is_apple()
+    @static if Sys.isapple()
         # if we didn't explicitly parse the weekday or year day, use mktime
         # to fill them in automatically.
         if !ismatch(r"([^%]|^)%(a|A|j|w|Ow)", fmt)
@@ -240,7 +240,7 @@ Get the local machine's host name.
 """
 function gethostname()
     hn = Vector{UInt8}(256)
-    err = @static if is_windows()
+    err = @static if Sys.iswindows()
         ccall(:gethostname, stdcall, Int32, (Ptr{UInt8}, UInt32), hn, length(hn))
     else
         ccall(:gethostname, Int32, (Ptr{UInt8}, UInt), hn, length(hn))
@@ -286,7 +286,7 @@ Convert a Win32 system call error code to a descriptive string [only available o
 """
 function FormatMessage end
 
-if is_windows()
+if Sys.iswindows()
     GetLastError() = ccall(:GetLastError, stdcall, UInt32, ())
 
     function FormatMessage(e=GetLastError())
diff --git a/base/libdl.jl b/base/libdl.jl
index 439b10bb40410..31d49840cf1b0 100644
--- a/base/libdl.jl
+++ b/base/libdl.jl
@@ -13,7 +13,7 @@ When calling [`dlopen`](@ref), the paths in this list will be searched first, in
 order, before searching the system locations for a valid library handle.
 """
 const DL_LOAD_PATH = String[]
-if is_apple()
+if Sys.isapple()
     push!(DL_LOAD_PATH, "@loader_path/julia")
     push!(DL_LOAD_PATH, "@loader_path")
 end
@@ -152,7 +152,7 @@ find_library(libname::Union{Symbol,AbstractString}, extrapaths=String[]) =
 function dlpath(handle::Ptr{Void})
     p = ccall(:jl_pathname_for_handle, Cstring, (Ptr{Void},), handle)
     s = unsafe_string(p)
-    is_windows() && Libc.free(p)
+    Sys.iswindows() && Libc.free(p)
     return s
 end
 
@@ -163,12 +163,12 @@ function dlpath(libname::Union{AbstractString, Symbol})
     return path
 end
 
-if is_apple()
+if Sys.isapple()
     const dlext = "dylib"
-elseif is_windows()
+elseif Sys.iswindows()
     const dlext = "dll"
 else
-    #assume is_linux, or similar
+    #assume Sys.islinux, or similar
     const dlext = "so"
 end
 
@@ -179,7 +179,7 @@ File extension for dynamic libraries (e.g. dll, dylib, so) on the current platfo
 """
 dlext
 
-if is_linux()
+if Sys.islinux()
     struct dl_phdr_info
         # Base address of object
         addr::Cuint
@@ -205,7 +205,7 @@ if is_linux()
     end
 end # linux-only
 
-if is_bsd() && !is_apple()
+if Sys.isbsd() && !Sys.isapple()
     # DL_ITERATE_PHDR(3) on freebsd
     struct dl_phdr_info
         # Base address of object
@@ -233,13 +233,13 @@ end # bsd family
 function dllist()
     dynamic_libraries = Vector{AbstractString}(0)
 
-    @static if is_linux()
+    @static if Sys.islinux()
         const callback = cfunction(dl_phdr_info_callback, Cint,
                                    (Ref{dl_phdr_info}, Csize_t, Ref{Array{AbstractString,1}} ))
         ccall(:dl_iterate_phdr, Cint, (Ptr{Void}, Ref{Array{AbstractString,1}}), callback, dynamic_libraries)
     end
 
-    @static if is_apple()
+    @static if Sys.isapple()
         numImages = ccall(:_dyld_image_count, Cint, ())
 
         # start at 1 instead of 0 to skip self
@@ -249,11 +249,11 @@ function dllist()
         end
     end
 
-    @static if is_windows()
+    @static if Sys.iswindows()
         ccall(:jl_dllist, Cint, (Any,), dynamic_libraries)
     end
 
-    @static if is_bsd() && !is_apple()
+    @static if Sys.isbsd() && !Sys.isapple()
         const callback = cfunction(dl_phdr_info_callback, Cint,
                                    (Ref{dl_phdr_info}, Csize_t, Ref{Array{AbstractString,1}} ))
         ccall(:dl_iterate_phdr, Cint, (Ptr{Void}, Ref{Array{AbstractString,1}}), callback, dynamic_libraries)
diff --git a/base/libgit2/callbacks.jl b/base/libgit2/callbacks.jl
index 0a78f48949f47..62a0905a0cc80 100644
--- a/base/libgit2/callbacks.jl
+++ b/base/libgit2/callbacks.jl
@@ -109,7 +109,7 @@ function authenticate_ssh(creds::SSHCredentials, libgit2credptr::Ptr{Ptr{Void}},
         else
             passdef = creds.pass # check if credentials were already used
             if passphrase_required && (isempty(passdef) || isusedcreds)
-                if is_windows()
+                if Sys.iswindows()
                     passdef = Base.winprompt(
                         "Your SSH Key requires a password, please enter it now:",
                         "Passphrase required", privatekey; prompt_username = false)
@@ -144,7 +144,7 @@ function authenticate_userpass(creds::UserPasswordCredentials, libgit2credptr::P
     if creds.prompt_if_incorrect
         username = creds.user
         userpass = creds.pass
-        if is_windows()
+        if Sys.iswindows()
             if isempty(username) || isempty(userpass) || isusedcreds
                 res = Base.winprompt("Please enter your credentials for '$schema$host'", "Credentials required",
                         isempty(username) ? urlusername : username; prompt_username = true)
diff --git a/base/libgit2/libgit2.jl b/base/libgit2/libgit2.jl
index bfc18a85f5bbd..94d4cb23a2bdb 100644
--- a/base/libgit2/libgit2.jl
+++ b/base/libgit2/libgit2.jl
@@ -886,7 +886,7 @@ function __init__()
     # windows and macOS use the OS native security backends
     old_ssl_cert_dir = Base.get(ENV, "SSL_CERT_DIR", nothing)
     old_ssl_cert_file = Base.get(ENV, "SSL_CERT_FILE", nothing)
-    @static if is_linux()
+    @static if Sys.islinux()
         cert_loc = if "SSL_CERT_DIR" in keys(ENV)
             ENV["SSL_CERT_DIR"]
         elseif "SSL_CERT_FILE" in keys(ENV)
@@ -909,7 +909,7 @@ function __init__()
         end
     end
 
-    @static if is_linux()
+    @static if Sys.islinux()
         if old_ssl_cert_dir != Base.get(ENV, "SSL_CERT_DIR", "")
             if old_ssl_cert_dir === nothing
                 delete!(ENV, "SSL_CERT_DIR")
diff --git a/base/libgit2/repository.jl b/base/libgit2/repository.jl
index c57353ffcbafb..3cf3295c55f90 100644
--- a/base/libgit2/repository.jl
+++ b/base/libgit2/repository.jl
@@ -19,7 +19,7 @@ Open a git repository at `path` with extended controls (for instance, if the cur
 user must be a member of a special access group to read `path`).
 """
 function GitRepoExt(path::AbstractString, flags::Cuint = Cuint(Consts.REPOSITORY_OPEN_DEFAULT))
-    separator = @static is_windows() ? ";" : ":"
+    separator = @static Sys.iswindows() ? ";" : ":"
     repo_ptr_ptr = Ref{Ptr{Void}}(C_NULL)
     @check ccall((:git_repository_open_ext, :libgit2), Cint,
                  (Ptr{Ptr{Void}}, Cstring, Cuint, Cstring),
diff --git a/base/libgit2/utils.jl b/base/libgit2/utils.jl
index 59b84bf905427..8f3002e7d85eb 100644
--- a/base/libgit2/utils.jl
+++ b/base/libgit2/utils.jl
@@ -32,7 +32,7 @@ reset(val::Integer, flag::Integer) = (val &= ~flag)
 toggle(val::Integer, flag::Integer) = (val |= flag)
 
 function prompt(msg::AbstractString; default::AbstractString="", password::Bool=false)
-    if is_windows() && password
+    if Sys.iswindows() && password
         error("Command line prompt not supported for password entry on windows. Use winprompt instead")
     end
     msg = !isempty(default) ? msg*" [$default]:" : msg*":"
@@ -60,8 +60,8 @@ end
 Standardise the path string `path` to use POSIX separators.
 """
 function posixpath end
-if is_windows()
+if Sys.iswindows()
     posixpath(path) = replace(path,'\\','/')
-else is_unix()
+else Sys.isunix()
     posixpath(path) = path
 end
diff --git a/base/linalg/blas.jl b/base/linalg/blas.jl
index eb2e5468ff392..cc0fd287a0c6e 100644
--- a/base/linalg/blas.jl
+++ b/base/linalg/blas.jl
@@ -105,7 +105,7 @@ function set_num_threads(n::Integer)
     end
 
     # OSX BLAS looks at an environment variable
-    @static if is_apple()
+    @static if Sys.isapple()
         ENV["VECLIB_MAXIMUM_THREADS"] = n
     end
 
diff --git a/base/loading.jl b/base/loading.jl
index 307611b6d5481..cf306d77ad24e 100644
--- a/base/loading.jl
+++ b/base/loading.jl
@@ -4,16 +4,16 @@
 
 # Cross-platform case-sensitive path canonicalization
 
-if is_unix() && !is_apple()
+if Sys.isunix() && !Sys.isapple()
     # assume case-sensitive filesystems, don't have to do anything
     isfile_casesensitive(path) = isfile(path)
-elseif is_windows()
+elseif Sys.iswindows()
     # GetLongPathName Win32 function returns the case-preserved filename on NTFS.
     function isfile_casesensitive(path)
         isfile(path) || return false  # Fail fast
         basename(Filesystem.longpath(path)) == basename(path)
     end
-elseif is_apple()
+elseif Sys.isapple()
     # HFS+ filesystem is case-preserving. The getattrlist API returns
     # a case-preserved filename. In the rare event that HFS+ is operating
     # in case-sensitive mode, this will still work but will be redundant.
diff --git a/base/methodshow.jl b/base/methodshow.jl
index 8600e95d009eb..598a9e5a7c795 100644
--- a/base/methodshow.jl
+++ b/base/methodshow.jl
@@ -194,7 +194,7 @@ function url(m::Method)
     file = string(m.file)
     line = m.line
     line <= 0 || ismatch(r"In\[[0-9]+\]", file) && return ""
-    is_windows() && (file = replace(file, '\\', '/'))
+    Sys.iswindows() && (file = replace(file, '\\', '/'))
     if inbase(M)
         if isempty(Base.GIT_VERSION_INFO.commit)
             # this url will only work if we're on a tagged release
diff --git a/base/mmap.jl b/base/mmap.jl
index eaac57e30b4df..d7e0a4a18a39a 100644
--- a/base/mmap.jl
+++ b/base/mmap.jl
@@ -2,7 +2,7 @@
 
 module Mmap
 
-const PAGESIZE = Int(is_unix() ? ccall(:jl_getpagesize, Clong, ()) : ccall(:jl_getallocationgranularity, Clong, ()))
+const PAGESIZE = Int(Sys.isunix() ? ccall(:jl_getpagesize, Clong, ()) : ccall(:jl_getallocationgranularity, Clong, ()))
 
 # for mmaps not backed by files
 mutable struct Anonymous <: IO
@@ -21,13 +21,13 @@ const INVALID_HANDLE_VALUE = -1
 gethandle(io::Anonymous) = INVALID_HANDLE_VALUE
 
 # platform-specific mmap utilities
-if is_unix()
+if Sys.isunix()
 
 const PROT_READ     = Cint(1)
 const PROT_WRITE    = Cint(2)
 const MAP_SHARED    = Cint(1)
 const MAP_PRIVATE   = Cint(2)
-const MAP_ANONYMOUS = Cint(is_bsd() ? 0x1000 : 0x20)
+const MAP_ANONYMOUS = Cint(Sys.isbsd() ? 0x1000 : 0x20)
 const F_GETFL       = Cint(3)
 
 gethandle(io::IO) = fd(io)
@@ -65,7 +65,7 @@ function grow!(io::IO, offset::Integer, len::Integer)
     return
 end
 
-elseif is_windows()
+elseif Sys.iswindows()
 
 const DWORD = Culong
 
@@ -116,7 +116,7 @@ function mmap(io::IO,
 
     file_desc = gethandle(io)
     # platform-specific mmapping
-    @static if is_unix()
+    @static if Sys.isunix()
         prot, flags, iswrite = settings(file_desc, shared)
         iswrite && grow && grow!(io, offset, len)
         # mmap the file
@@ -138,7 +138,7 @@ function mmap(io::IO,
     # convert mmapped region to Julia Array at `ptr + (offset - offset_page)` since file was mapped at offset_page
     A = unsafe_wrap(Array, convert(Ptr{T}, UInt(ptr) + UInt(offset - offset_page)), dims)
     finalizer(A, function(x)
-        @static if is_unix()
+        @static if Sys.isunix()
             systemerror("munmap",  ccall(:munmap, Cint, (Ptr{Void}, Int), ptr, mmaplen) != 0)
         else
             status = ccall(:UnmapViewOfFile, stdcall, Cint, (Ptr{Void},), ptr)!=0
@@ -207,7 +207,7 @@ const MS_SYNC = 4
 function sync!(m::Array{T}, flags::Integer=MS_SYNC) where T
     offset = rem(UInt(pointer(m)), PAGESIZE)
     ptr = pointer(m) - offset
-    @static if is_unix()
+    @static if Sys.isunix()
         systemerror("msync",
                     ccall(:msync, Cint, (Ptr{Void}, Csize_t, Cint), ptr, length(m) * sizeof(T), flags) != 0)
     else
diff --git a/base/osutils.jl b/base/osutils.jl
index a37f51c5f0db2..96b6434d7e0ab 100644
--- a/base/osutils.jl
+++ b/base/osutils.jl
@@ -1,62 +1,15 @@
 # This file is a part of Julia. License is MIT: https://julialang.org/license
 
-"""
-    is_unix([os])
-
-Predicate for testing if the OS provides a Unix-like interface.
-See documentation in [Handling Operating System Variation](@ref).
-"""
-function is_unix(os::Symbol)
-    if is_windows(os)
-        return false
-    elseif is_linux(os) || is_bsd(os)
-        return true
-    else
-        throw(ArgumentError("unknown operating system \"$os\""))
-    end
-end
-
-"""
-    is_linux([os])
-
-Predicate for testing if the OS is a derivative of Linux.
-See documentation in [Handling Operating System Variation](@ref).
-"""
-is_linux(os::Symbol) = (os == :Linux)
-
-"""
-    is_bsd([os])
-
-Predicate for testing if the OS is a derivative of BSD.
-See documentation in [Handling Operating System Variation](@ref).
-"""
-is_bsd(os::Symbol) = (os == :FreeBSD || os == :OpenBSD || os == :NetBSD || os == :DragonFly || os == :Darwin || os == :Apple)
-
-"""
-    is_windows([os])
-
-Predicate for testing if the OS is a derivative of Microsoft Windows NT.
-See documentation in [Handling Operating System Variation](@ref).
-"""
-is_windows(os::Symbol) = (os == :Windows || os == :NT)
-
-"""
-    is_apple([os])
-
-Predicate for testing if the OS is a derivative of Apple Macintosh OS X or Darwin.
-See documentation in [Handling Operating System Variation](@ref).
-"""
-is_apple(os::Symbol) = (os == :Apple || os == :Darwin)
-
 """
     @static
 
-Partially evaluates an expression at parse time.
+Partially evaluate an expression at parse time.
 
-For example, `@static is_windows() ? foo : bar` will evaluate `is_windows()` and insert either `foo` or `bar` into the expression.
+For example, `@static Sys.iswindows() ? foo : bar` will evaluate `Sys.iswindows()` and insert
+either `foo` or `bar` into the expression.
 This is useful in cases where a construct would be invalid on other platforms,
 such as a `ccall` to a non-existent function.
-`@static if is_apple() foo end` and `@static foo <&&,||> bar` are also valid syntax.
+`@static if Sys.isapple() foo end` and `@static foo <&&,||> bar` are also valid syntax.
 """
 macro static(ex)
     if isa(ex, Expr)
@@ -75,13 +28,3 @@ macro static(ex)
     end
     throw(ArgumentError("invalid @static macro"))
 end
-
-let KERNEL = ccall(:jl_get_UNAME, Any, ()),
-    __module__ = @__MODULE__
-    # evaluate the zero-argument form of each of these functions
-    # as a function returning a static constant based on the build-time
-    # operating-system kernel
-    for f in (:is_unix, :is_linux, :is_bsd, :is_apple, :is_windows)
-        @eval $f() = $(getfield(__module__, f)(KERNEL))
-    end
-end
diff --git a/base/path.jl b/base/path.jl
index 940ae4cd2d6e0..c042bef833e1f 100644
--- a/base/path.jl
+++ b/base/path.jl
@@ -16,7 +16,7 @@ export
     splitdrive,
     splitext
 
-if is_unix()
+if Sys.isunix()
     const path_separator    = "/"
     const path_separator_re = r"/+"
     const path_directory_re = r"(?:^|/)\.{0,2}$"
@@ -24,7 +24,7 @@ if is_unix()
     const path_ext_splitter = r"^((?:.*/)?(?:\.|[^/\.])[^/]*?)(\.[^/\.]*|)$"
 
     splitdrive(path::String) = ("",path)
-elseif is_windows()
+elseif Sys.iswindows()
     const path_separator    = "\\"
     const path_separator_re = r"[/\\]+"
     const path_absolute_re  = r"^(?:\w+:)?[/\\]"
@@ -77,7 +77,7 @@ function homedir()
 end
 
 
-if is_windows()
+if Sys.iswindows()
     isabspath(path::String) = ismatch(path_absolute_re, path)
 else
     isabspath(path::String) = startswith(path, '/')
@@ -276,7 +276,7 @@ current directory if necessary. Equivalent to `abspath(joinpath(path, paths...))
 """
 abspath(a::AbstractString, b::AbstractString...) = abspath(joinpath(a,b...))
 
-if is_windows()
+if Sys.iswindows()
 function realpath(path::AbstractString)
     p = cwstring(path)
     buf = zeros(UInt16, length(p))
@@ -324,7 +324,7 @@ Canonicalize a path by expanding symbolic links and removing "." and ".." entrie
 realpath(path::AbstractString)
 
 
-if is_windows()
+if Sys.iswindows()
 expanduser(path::AbstractString) = path # on windows, ~ means "temporary file"
 else
 function expanduser(path::AbstractString)
diff --git a/base/pkg/cache.jl b/base/pkg/cache.jl
index 1a1a766f9cddc..db9d2426c4704 100644
--- a/base/pkg/cache.jl
+++ b/base/pkg/cache.jl
@@ -18,7 +18,7 @@ function mkcachedir()
         return
     end
 
-    @static if is_unix()
+    @static if Sys.isunix()
         if Dir.isversioned(pwd())
             rootcache = joinpath(realpath(".."), ".cache")
             if !isdir(rootcache)
diff --git a/base/pkg/reqs.jl b/base/pkg/reqs.jl
index 286f64d481ed5..e424bca9fcd30 100644
--- a/base/pkg/reqs.jl
+++ b/base/pkg/reqs.jl
@@ -90,16 +90,16 @@ function parse(lines::Vector{Line})
         if isa(line,Requirement)
             if !isempty(line.system)
                 applies = false
-                if is_windows(); applies |=  ("windows"  in line.system); end
-                if is_unix();    applies |=  ("unix"     in line.system); end
-                if is_apple();   applies |=  ("osx"      in line.system); end
-                if is_linux();   applies |=  ("linux"    in line.system); end
-                if is_bsd();     applies |=  ("bsd"      in line.system); end
-                if is_windows(); applies &= !("!windows" in line.system); end
-                if is_unix();    applies &= !("!unix"    in line.system); end
-                if is_apple();   applies &= !("!osx"     in line.system); end
-                if is_linux();   applies &= !("!linux"   in line.system); end
-                if is_bsd();     applies &= !("!bsd"     in line.system); end
+                if Sys.iswindows(); applies |=  ("windows"  in line.system); end
+                if Sys.isunix();    applies |=  ("unix"     in line.system); end
+                if Sys.isapple();   applies |=  ("osx"      in line.system); end
+                if Sys.islinux();   applies |=  ("linux"    in line.system); end
+                if Sys.isbsd();     applies |=  ("bsd"      in line.system); end
+                if Sys.iswindows(); applies &= !("!windows" in line.system); end
+                if Sys.isunix();    applies &= !("!unix"    in line.system); end
+                if Sys.isapple();   applies &= !("!osx"     in line.system); end
+                if Sys.islinux();   applies &= !("!linux"   in line.system); end
+                if Sys.isbsd();     applies &= !("!bsd"     in line.system); end
                 applies || continue
             end
             reqs[line.package] = haskey(reqs, line.package) ?
diff --git a/base/pkg/types.jl b/base/pkg/types.jl
index 1e55a0b308694..c04fd1a92a119 100644
--- a/base/pkg/types.jl
+++ b/base/pkg/types.jl
@@ -82,8 +82,8 @@ VersionSet(versions::VersionNumber...) = VersionSet(VersionNumber[versions...])
 const empty_versionset = VersionSet(VersionInterval[])
 
 # Windows console doesn't like Unicode
-const _empty_symbol = @static is_windows() ? "empty" : "∅"
-const _union_symbol = @static is_windows() ? " or " : " ∪ "
+const _empty_symbol = @static Sys.iswindows() ? "empty" : "∅"
+const _union_symbol = @static Sys.iswindows() ? " or " : " ∪ "
 show(io::IO, s::VersionSet) = isempty(s) ? print(io, _empty_symbol) :
                                            join(io, s.intervals, _union_symbol)
 isempty(s::VersionSet) = all(isempty, s.intervals)
diff --git a/base/poll.jl b/base/poll.jl
index a670a10f0a979..e53b5892dd1bf 100644
--- a/base/poll.jl
+++ b/base/poll.jl
@@ -13,7 +13,7 @@ export
 import Base: @handle_as, wait, close, uvfinalize, eventloop, notify_error, stream_wait,
     _sizeof_uv_poll, _sizeof_uv_fs_poll, _sizeof_uv_fs_event, _uv_hook_close,
     associate_julia_struct, disassociate_julia_struct, |
-if is_windows()
+if Sys.iswindows()
     import Base.WindowsRawSocket
 end
 
@@ -106,7 +106,7 @@ mutable struct _FDWatcher
 
     let FDWatchers = Vector{Any}()
         global _FDWatcher
-        @static if is_unix()
+        @static if Sys.isunix()
             function _FDWatcher(fd::RawFD, readable::Bool, writable::Bool)
                 if !readable && !writable
                     throw(ArgumentError("must specify at least one of readable or writable to create a FDWatcher"))
@@ -154,7 +154,7 @@ mutable struct _FDWatcher
             end
             t.refcount = (0, 0)
             t.active = (false, false)
-            @static if is_unix()
+            @static if Sys.isunix()
                 if FDWatchers[t.fdnum] == t
                     FDWatchers[t.fdnum] = nothing
                 end
@@ -164,7 +164,7 @@ mutable struct _FDWatcher
         end
     end
 
-    @static if is_windows()
+    @static if Sys.iswindows()
         function _FDWatcher(fd::RawFD, readable::Bool, writable::Bool)
             handle = Libc._get_osfhandle(fd)
             return _FDWatcher(handle, readable, writable)
@@ -205,7 +205,7 @@ mutable struct FDWatcher
         finalizer(this, close)
         return this
     end
-    @static if is_windows()
+    @static if Sys.iswindows()
         function FDWatcher(fd::WindowsRawSocket, readable::Bool, writable::Bool)
             this = new(_FDWatcher(fd, readable, writable), readable, writable)
             finalizer(this, close)
@@ -406,7 +406,7 @@ function wait(fd::RawFD; readable=false, writable=false)
     end
 end
 
-if is_windows()
+if Sys.iswindows()
     function wait(socket::WindowsRawSocket; readable=false, writable=false)
         fdw = _FDWatcher(socket, readable, writable)
         try
@@ -443,7 +443,7 @@ least one of them must be set to `true`.
 The returned value is an object with boolean fields `readable`, `writable`, and `timedout`,
 giving the result of the polling.
 """
-function poll_fd(s::Union{RawFD, is_windows() ? WindowsRawSocket : Union{}}, timeout_s::Real=-1; readable=false, writable=false)
+function poll_fd(s::Union{RawFD, Sys.iswindows() ? WindowsRawSocket : Union{}}, timeout_s::Real=-1; readable=false, writable=false)
     wt = Condition()
     fdw = _FDWatcher(s, readable, writable)
     try
diff --git a/base/process.jl b/base/process.jl
index ea421ce4e729f..e4068caec9f97 100644
--- a/base/process.jl
+++ b/base/process.jl
@@ -136,7 +136,7 @@ struct FileRedirect
     filename::AbstractString
     append::Bool
     function FileRedirect(filename, append)
-        if lowercase(filename) == (@static is_windows() ? "nul" : "/dev/null")
+        if lowercase(filename) == (@static Sys.iswindows() ? "nul" : "/dev/null")
             warn_once("for portability use DevNull instead of a file redirect")
         end
         new(filename, append)
diff --git a/base/profile.jl b/base/profile.jl
index a5afcb3fdfb62..922ec8414b805 100644
--- a/base/profile.jl
+++ b/base/profile.jl
@@ -60,7 +60,7 @@ end
 
 # init with default values
 # Use a max size of 1M profile samples, and fire timer every 1ms
-if is_windows()
+if Sys.iswindows()
     __init__() = init(1_000_000, 0.01)
 else
     __init__() = init(1_000_000, 0.001)
diff --git a/base/random.jl b/base/random.jl
index 4375a3c7ea1ee..4e0f7f25d4ff1 100644
--- a/base/random.jl
+++ b/base/random.jl
@@ -28,7 +28,7 @@ mutable struct Close1Open2 <: FloatInterval end
 
 ## RandomDevice
 
-if is_windows()
+if Sys.iswindows()
 
     struct RandomDevice <: AbstractRNG
         buffer::Vector{UInt128}
diff --git a/base/repl/LineEdit.jl b/base/repl/LineEdit.jl
index 4beccbff1841b..941a184ce0743 100644
--- a/base/repl/LineEdit.jl
+++ b/base/repl/LineEdit.jl
@@ -201,7 +201,7 @@ function refresh_multi_line(termbuf::TerminalBuffer, terminal::UnixTerminal, buf
     write_prompt(termbuf, prompt)
     prompt = prompt_string(prompt)
     # Count the '\n' at the end of the line if the terminal emulator does (specific to DOS cmd prompt)
-    miscountnl = @static is_windows() ? (isa(Terminals.pipe_reader(terminal), Base.TTY) && !Base.ispty(Terminals.pipe_reader(terminal))) : false
+    miscountnl = @static Sys.iswindows() ? (isa(Terminals.pipe_reader(terminal), Base.TTY) && !Base.ispty(Terminals.pipe_reader(terminal))) : false
     lindent = strwidth(prompt)
 
     # Now go through the buffer line by line
@@ -1574,7 +1574,7 @@ function run_interface(terminal, m::ModalInterface)
     while !s.aborted
         buf, ok, suspend = prompt!(terminal, m, s)
         while suspend
-            @static if is_unix(); ccall(:jl_repl_raise_sigtstp, Cint, ()); end
+            @static if Sys.isunix(); ccall(:jl_repl_raise_sigtstp, Cint, ()); end
             buf, ok, suspend = prompt!(terminal, m, s)
         end
         eval(Main,
@@ -1626,7 +1626,7 @@ function prompt!(term, prompt, s = init_state(term, prompt))
             elseif state === :done
                 return buffer(s), true, false
             elseif state === :suspend
-                if is_unix()
+                if Sys.isunix()
                     return buffer(s), true, true
                 end
             else
diff --git a/base/repl/REPLCompletions.jl b/base/repl/REPLCompletions.jl
index 4a80c24991cf3..4ae598183224d 100644
--- a/base/repl/REPLCompletions.jl
+++ b/base/repl/REPLCompletions.jl
@@ -101,7 +101,7 @@ function complete_keyword(s::String)
 end
 
 function complete_path(path::AbstractString, pos; use_envpath=false)
-    if Base.is_unix() && ismatch(r"^~(?:/|$)", path)
+    if Base.Sys.isunix() && ismatch(r"^~(?:/|$)", path)
         # if the path is just "~", don't consider the expanded username as a prefix
         if path == "~"
             dir, prefix = homedir(), ""
@@ -129,13 +129,13 @@ function complete_path(path::AbstractString, pos; use_envpath=false)
         if startswith(file, prefix)
             id = try isdir(joinpath(dir, file)) catch; false end
             # joinpath is not used because windows needs to complete with double-backslash
-            push!(matches, id ? file * (@static is_windows() ? "\\\\" : "/") : file)
+            push!(matches, id ? file * (@static Sys.iswindows() ? "\\\\" : "/") : file)
         end
     end
 
     if use_envpath && length(dir) == 0
         # Look for files in PATH as well
-        local pathdirs = split(ENV["PATH"], @static is_windows() ? ";" : ":")
+        local pathdirs = split(ENV["PATH"], @static Sys.iswindows() ? ";" : ":")
 
         for pathdir in pathdirs
             local actualpath
diff --git a/base/repl/Terminals.jl b/base/repl/Terminals.jl
index 29dd5e88e4e93..ad7382009d832 100644
--- a/base/repl/Terminals.jl
+++ b/base/repl/Terminals.jl
@@ -120,7 +120,7 @@ cmove_line_up(t::UnixTerminal, n) = (cmove_up(t, n); cmove_col(t, 1))
 cmove_line_down(t::UnixTerminal, n) = (cmove_down(t, n); cmove_col(t, 1))
 cmove_col(t::UnixTerminal, n) = (write(t.out_stream, '\r'); n > 1 && cmove_right(t, n-1))
 
-if is_windows()
+if Sys.iswindows()
     function raw!(t::TTYTerminal,raw::Bool)
         check_open(t.in_stream)
         if Base.ispty(t.in_stream)
@@ -150,7 +150,7 @@ end
 
 Base.displaysize(t::UnixTerminal) = displaysize(t.out_stream)
 
-if is_windows()
+if Sys.iswindows()
     hascolor(t::TTYTerminal) = true
 else
     function hascolor(t::TTYTerminal)
diff --git a/base/serialize.jl b/base/serialize.jl
index b8e2387e98d00..2e1de356aed21 100644
--- a/base/serialize.jl
+++ b/base/serialize.jl
@@ -1106,7 +1106,7 @@ function deserialize(s::AbstractSerializer, t::Type{Regex})
     Regex(pattern, compile_options, match_options)
 end
 
-if !is_windows()
+if !Sys.iswindows()
     function serialize(s::AbstractSerializer, rd::RandomDevice)
         serialize_type(s, typeof(rd))
         serialize(s, rd.unlimited)
diff --git a/base/sharedarray.jl b/base/sharedarray.jl
index 6ef164720b836..470a4199965fd 100644
--- a/base/sharedarray.jl
+++ b/base/sharedarray.jl
@@ -579,9 +579,9 @@ end
 
 function print_shmem_limits(slen)
     try
-        if is_linux()
+        if Sys.islinux()
             pfx = "kernel"
-        elseif is_apple()
+        elseif Sys.isapple()
             pfx = "kern.sysv"
         elseif Sys.KERNEL == :FreeBSD || Sys.KERNEL == :DragonFly
             pfx = "kern.ipc"
@@ -633,7 +633,7 @@ end
 
 # platform-specific code
 
-if is_windows()
+if Sys.iswindows()
 function _shm_mmap_array(T, dims, shm_seg_name, mode)
     readonly = !((mode & JL_O_RDWR) == JL_O_RDWR)
     create = (mode & JL_O_CREAT) == JL_O_CREAT
diff --git a/base/socket.jl b/base/socket.jl
index d5af99ca9c57e..fd1298fdb5f9f 100644
--- a/base/socket.jl
+++ b/base/socket.jl
@@ -875,9 +875,9 @@ function _sockname(sock, self=true)
     uv_error("cannot obtain socket name", r)
     if r == 0
         port = ntoh(rport[])
-        af_inet6 = @static if is_windows() # AF_INET6 in <sys/socket.h>
+        af_inet6 = @static if Sys.iswindows() # AF_INET6 in <sys/socket.h>
             23
-        elseif is_apple()
+        elseif Sys.isapple()
             30
         elseif Sys.KERNEL ∈ (:FreeBSD, :DragonFly)
             28
diff --git a/base/stream.jl b/base/stream.jl
index 9d24313c24fc5..5b5bdaa28fa48 100644
--- a/base/stream.jl
+++ b/base/stream.jl
@@ -1,7 +1,7 @@
 # This file is a part of Julia. License is MIT: https://julialang.org/license
 
 import .Libc: RawFD, dup
-if is_windows()
+if Sys.iswindows()
     import .Libc: WindowsRawSocket
 end
 
@@ -159,7 +159,7 @@ mutable struct TTY <: LibuvStream
     sendbuf::Nullable{IOBuffer}
     lock::ReentrantLock
     throttle::Int
-    @static if is_windows(); ispty::Bool; end
+    @static if Sys.iswindows(); ispty::Bool; end
     TTY() = TTY(Libc.malloc(_sizeof_uv_tty), StatusUninit)
     function TTY(handle::Ptr{Void}, status)
         tty = new(
@@ -172,7 +172,7 @@ mutable struct TTY <: LibuvStream
             DEFAULT_READ_BUFFER_SZ)
         associate_julia_struct(handle, tty)
         finalizer(tty, uvfinalize)
-        @static if is_windows()
+        @static if Sys.iswindows()
             tty.ispty = ccall(:jl_ispty, Cint, (Ptr{Void},), handle) != 0
         end
         return tty
@@ -343,7 +343,7 @@ function uvfinalize(uv::Union{LibuvStream, LibuvServer})
     nothing
 end
 
-if is_windows()
+if Sys.iswindows()
     ispty(s::TTY) = s.ispty
     ispty(s::IO) = false
 end
@@ -358,7 +358,7 @@ function displaysize(io::TTY)
     local h::Int, w::Int
     default_size = displaysize()
 
-    @static if is_windows()
+    @static if Sys.iswindows()
         if ispty(io)
             # io is actually a libuv pipe but a cygwin/msys2 pty
             try
@@ -676,7 +676,7 @@ function start_reading(stream::LibuvStream)
     end
 end
 
-if is_windows()
+if Sys.iswindows()
     # the low performance version of stop_reading is required
     # on Windows due to a NT kernel bug that we can't use a blocking
     # stream for non-blocking (overlapped) calls,
@@ -994,8 +994,8 @@ Connect to the named pipe / UNIX domain socket at `path`.
 """
 connect(path::AbstractString) = connect(init_pipe!(PipeEndpoint(); readable=false, writable=false, julia_only=true),path)
 
-const OS_HANDLE = is_windows() ? WindowsRawSocket : RawFD
-const INVALID_OS_HANDLE = is_windows() ? WindowsRawSocket(Ptr{Void}(-1)) : RawFD(-1)
+const OS_HANDLE = Sys.iswindows() ? WindowsRawSocket : RawFD
+const INVALID_OS_HANDLE = Sys.iswindows() ? WindowsRawSocket(Ptr{Void}(-1)) : RawFD(-1)
 _fd(x::IOStream) = RawFD(fd(x))
 function _fd(x::Union{LibuvStream, LibuvServer})
     fd = Ref{OS_HANDLE}(INVALID_OS_HANDLE)
@@ -1016,7 +1016,7 @@ for (x, writable, unix_fd, c_symbol) in
         function ($_f)(stream)
             global $x
             posix_fd = _fd(stream)
-            @static if is_windows()
+            @static if Sys.iswindows()
                 ccall(:SetStdHandle, stdcall, Int32, (Int32, Ptr{Void}),
                     $(-10 - unix_fd), Libc._get_osfhandle(posix_fd).handle)
             end
diff --git a/base/sysinfo.jl b/base/sysinfo.jl
index 95fc5ccb35f6b..fb6b1435e4ac6 100644
--- a/base/sysinfo.jl
+++ b/base/sysinfo.jl
@@ -14,7 +14,12 @@ export CPU_CORES,
        uptime,
        loadavg,
        free_memory,
-       total_memory
+       total_memory,
+       isapple,
+       isbsd,
+       islinux,
+       isunix,
+       iswindows
 
 import ..Base: show
 
@@ -190,7 +195,59 @@ end
 
 maxrss() = ccall(:jl_maxrss, Csize_t, ())
 
-if is_windows()
+"""
+    Sys.isunix([os])
+
+Predicate for testing if the OS provides a Unix-like interface.
+See documentation in [Handling Operating System Variation](@ref).
+"""
+function isunix(os::Symbol)
+    if iswindows(os)
+        return false
+    elseif islinux(os) || isbsd(os)
+        return true
+    else
+        throw(ArgumentError("unknown operating system \"$os\""))
+    end
+end
+
+"""
+    Sys.islinux([os])
+
+Predicate for testing if the OS is a derivative of Linux.
+See documentation in [Handling Operating System Variation](@ref).
+"""
+islinux(os::Symbol) = (os == :Linux)
+
+"""
+    Sys.isbsd([os])
+
+Predicate for testing if the OS is a derivative of BSD.
+See documentation in [Handling Operating System Variation](@ref).
+"""
+isbsd(os::Symbol) = (os == :FreeBSD || os == :OpenBSD || os == :NetBSD || os == :DragonFly || os == :Darwin || os == :Apple)
+
+"""
+    Sys.iswindows([os])
+
+Predicate for testing if the OS is a derivative of Microsoft Windows NT.
+See documentation in [Handling Operating System Variation](@ref).
+"""
+iswindows(os::Symbol) = (os == :Windows || os == :NT)
+
+"""
+    Sys.isapple([os])
+
+Predicate for testing if the OS is a derivative of Apple Macintosh OS X or Darwin.
+See documentation in [Handling Operating System Variation](@ref).
+"""
+isapple(os::Symbol) = (os == :Apple || os == :Darwin)
+
+for f in (:isunix, :islinux, :isbsd, :isapple, :iswindows)
+    @eval $f() = $(getfield(@__MODULE__, f)(KERNEL))
+end
+
+if iswindows()
     function windows_version()
         verinfo = ccall(:GetVersion, UInt32, ())
         VersionNumber(verinfo & 0xFF, (verinfo >> 8) & 0xFF, verinfo >> 16)
diff --git a/base/util.jl b/base/util.jl
index 4f248941725ff..413b304fb0ab4 100644
--- a/base/util.jl
+++ b/base/util.jl
@@ -619,9 +619,9 @@ end
 
 function julia_exename()
     if ccall(:jl_is_debugbuild, Cint, ()) == 0
-        return @static is_windows() ? "julia.exe" : "julia"
+        return @static Sys.iswindows() ? "julia.exe" : "julia"
     else
-        return @static is_windows() ? "julia-debug.exe" : "julia-debug"
+        return @static Sys.iswindows() ? "julia-debug.exe" : "julia-debug"
     end
 end
 
@@ -640,7 +640,7 @@ securezero!(s::String) = unsafe_securezero!(pointer(s), sizeof(s))
     ccall(:memset, Ptr{T}, (Ptr{T}, Cint, Csize_t), p, 0, len*sizeof(T))
 unsafe_securezero!(p::Ptr{Void}, len::Integer=1) = Ptr{Void}(unsafe_securezero!(Ptr{UInt8}(p), len))
 
-if is_windows()
+if Sys.iswindows()
 function getpass(prompt::AbstractString)
     print(prompt)
     flush(STDOUT)
@@ -673,7 +673,7 @@ getpass(prompt::AbstractString) = unsafe_string(ccall(:getpass, Cstring, (Cstrin
 end
 
 # Windows authentication prompt
-if is_windows()
+if Sys.iswindows()
     struct CREDUI_INFO
         cbSize::UInt32
         parent::Ptr{Void}
diff --git a/contrib/build_sysimg.jl b/contrib/build_sysimg.jl
index 7ca643f9204b5..762deb7e6a094 100644
--- a/contrib/build_sysimg.jl
+++ b/contrib/build_sysimg.jl
@@ -5,7 +5,7 @@
 # userimg_path.  If sysimg_path.dlext is currently loaded into memory, don't continue
 # unless force is set to true.  Allow targeting of a CPU architecture via cpu_target.
 function default_sysimg_path(debug=false)
-    if is_unix()
+    if Sys.isunix()
         splitext(Libdl.dlpath(debug ? "sys-debug" : "sys"))[1]
     else
         joinpath(dirname(JULIA_HOME), "lib", "julia", debug ? "sys-debug" : "sys")
@@ -114,7 +114,7 @@ function find_system_compiler()
     end
 
     # On Windows, check to see if WinRPM is installed, and if so, see if gcc is installed
-    if is_windows()
+    if Sys.iswindows()
         try
             eval(Main, :(using WinRPM))
             winrpmgcc = joinpath(WinRPM.installdir, "usr", "$(Sys.ARCH)-w64-mingw32",
@@ -151,7 +151,7 @@ function link_sysimg(sysimg_path=nothing, cc=find_system_compiler(), debug=false
 
     push!(FLAGS, "-shared")
     push!(FLAGS, debug ? "-ljulia-debug" : "-ljulia")
-    if is_windows()
+    if Sys.iswindows()
         push!(FLAGS, "-lssp")
     end
 
@@ -159,7 +159,7 @@ function link_sysimg(sysimg_path=nothing, cc=find_system_compiler(), debug=false
     info("Linking sys.$(Libdl.dlext)")
     info("$cc $(join(FLAGS, ' ')) -o $sysimg_file $sysimg_path.o")
     # Windows has difficulties overwriting a file in use so we first link to a temp file
-    if is_windows() && isfile(sysimg_file)
+    if Sys.iswindows() && isfile(sysimg_file)
         if success(pipeline(`$cc $FLAGS -o $sysimg_path.tmp $sysimg_path.o`; stdout=STDOUT, stderr=STDERR))
             mv(sysimg_file, "$sysimg_file.old"; remove_destination=true)
             mv("$sysimg_path.tmp", sysimg_file; remove_destination=true)
diff --git a/contrib/julia-config.jl b/contrib/julia-config.jl
index 2a177240d536f..b6536c283f145 100755
--- a/contrib/julia-config.jl
+++ b/contrib/julia-config.jl
@@ -35,9 +35,9 @@ end
 
 function ldflags()
     fl = "-L$(shell_escape(libDir()))"
-    if is_windows()
+    if Sys.iswindows()
         fl = fl * " -Wl,--stack,8388608"
-    elseif is_linux()
+    elseif Sys.islinux()
         fl = fl * " -Wl,--export-dynamic"
     end
     return fl
@@ -49,7 +49,7 @@ function ldlibs()
     else
         "julia"
     end
-    if is_unix()
+    if Sys.isunix()
         return "-Wl,-rpath,$(shell_escape(libDir())) -Wl,-rpath,$(shell_escape(private_libDir())) -l$libname"
     else
         return "-l$libname -lopenlibm"
@@ -64,7 +64,7 @@ function cflags()
     if threadingOn()
         print(flags, " -DJULIA_ENABLE_THREADING=1")
     end
-    if is_unix()
+    if Sys.isunix()
         print(flags, " -fPIC")
     end
     return String(take!(flags))
diff --git a/doc/src/manual/handling-operating-system-variation.md b/doc/src/manual/handling-operating-system-variation.md
index 5312afe7bc955..46ee1ae3a6f70 100644
--- a/doc/src/manual/handling-operating-system-variation.md
+++ b/doc/src/manual/handling-operating-system-variation.md
@@ -2,38 +2,38 @@
 
 When dealing with platform libraries, it is often necessary to provide special cases for various
 platforms. The variable `Sys.KERNEL` can be used to write these special cases. There are several
-functions intended to make this easier: `is_unix`, `is_linux`, `is_apple`, `is_bsd`, and `is_windows`.
-These may be used as follows:
+functions in the `Sys` module intended to make this easier: `isunix`, `islinux`, `isapple`,
+`isbsd`, and `iswindows`. These may be used as follows:
 
 ```julia
-if is_windows()
+if Sys.iswindows()
     some_complicated_thing(a)
 end
 ```
 
-Note that `is_linux` and `is_apple` are mutually exclusive subsets of `is_unix`. Additionally,
+Note that `islinux` and `isapple` are mutually exclusive subsets of `isunix`. Additionally,
 there is a macro `@static` which makes it possible to use these functions to conditionally hide
 invalid code, as demonstrated in the following examples.
 
 Simple blocks:
 
 ```
-ccall( (@static is_windows() ? :_fopen : :fopen), ...)
+ccall((@static Sys.iswindows() ? :_fopen : :fopen), ...)
 ```
 
 Complex blocks:
 
 ```julia
-@static if is_linux()
+@static if Sys.islinux()
     some_complicated_thing(a)
 else
     some_different_thing(a)
 end
 ```
 
-When chaining conditionals (including if/elseif/end), the `@static` must be repeated for each
-level (parentheses optional, but recommended for readability):
+When chaining conditionals (including `if`/`elseif`/`end`), the `@static` must be repeated for
+each level (parentheses optional, but recommended for readability):
 
 ```julia
-@static is_windows() ? :a : (@static is_apple() ? :b : :c)
+@static Sys.iswindows() ? :a : (@static Sys.isapple() ? :b : :c)
 ```
diff --git a/doc/src/stdlib/base.md b/doc/src/stdlib/base.md
index d17eb625344be..9b9b5875b5e23 100644
--- a/doc/src/stdlib/base.md
+++ b/doc/src/stdlib/base.md
@@ -189,11 +189,11 @@ Base.@elapsed
 Base.@allocated
 Base.EnvHash
 Base.ENV
-Base.is_unix
-Base.is_apple
-Base.is_linux
-Base.is_bsd
-Base.is_windows
+Base.Sys.isunix
+Base.Sys.isapple
+Base.Sys.islinux
+Base.Sys.isbsd
+Base.Sys.iswindows
 Base.Sys.windows_version
 Base.@static
 ```
diff --git a/test/TestHelpers.jl b/test/TestHelpers.jl
index 8debcba768ed8..044167ee349c3 100644
--- a/test/TestHelpers.jl
+++ b/test/TestHelpers.jl
@@ -20,7 +20,7 @@ Base.Terminals.raw!(t::FakeTerminal, raw::Bool) = t.raw = raw
 Base.Terminals.size(t::FakeTerminal) = (24, 80)
 
 function open_fake_pty()
-    @static if is_windows()
+    @static if Sys.iswindows()
         error("Unable to create a fake PTY in Windows")
     end
 
diff --git a/test/backtrace.jl b/test/backtrace.jl
index 3c4d5abfb1f57..c0ffa9a915c7c 100644
--- a/test/backtrace.jl
+++ b/test/backtrace.jl
@@ -49,7 +49,7 @@ catch err
 end
 
 # different-file inline
-const absfilepath = is_windows() ? "C:\\foo\\bar\\baz.jl" : "/foo/bar/baz.jl"
+const absfilepath = Sys.iswindows() ? "C:\\foo\\bar\\baz.jl" : "/foo/bar/baz.jl"
 eval(Expr(:function, Expr(:call, :test_inline_2),
           Expr(:block, Expr(:line, 81, Symbol("backtrace.jl")),
                        Expr(:block, Expr(:meta, :push_loc, Symbol(absfilepath)),
diff --git a/test/channels.jl b/test/channels.jl
index 7f5d206f99e70..27ddc30adb6f9 100644
--- a/test/channels.jl
+++ b/test/channels.jl
@@ -315,7 +315,7 @@ let tc = Ref(0),
     ccall(:uv_async_send, Void, (Ptr{Void},), async)
     Base.process_events(false) # schedule event
     ccall(:uv_async_send, Void, (Ptr{Void},), async)
-    is_windows() && Base.process_events(false) # schedule event (windows?)
+    Sys.iswindows() && Base.process_events(false) # schedule event (windows?)
     @test tc[] == 0
     yield() # consume event
     @test tc[] == 1
@@ -327,7 +327,7 @@ let tc = Ref(0),
     @test !isopen(async)
     @test tc[] == 1
     Base.process_events(false) # schedule event & then close
-    is_windows() && Base.process_events(false) # schedule event (windows?)
+    Sys.iswindows() && Base.process_events(false) # schedule event (windows?)
     yield() # consume event & then close
     @test tc[] == 2
     sleep(0.1) # no further events
@@ -342,7 +342,7 @@ let tc = Ref(0),
     close(async)
     @test !isopen(async)
     Base.process_events(false) # schedule event & then close
-    is_windows() && Base.process_events(false) # schedule event (windows)
+    Sys.iswindows() && Base.process_events(false) # schedule event (windows)
     @test tc[] == 0
     yield() # consume event & then close
     @test tc[] == 1
diff --git a/test/cmdlineargs.jl b/test/cmdlineargs.jl
index fc54c1781bd0e..a70a494f51b69 100644
--- a/test/cmdlineargs.jl
+++ b/test/cmdlineargs.jl
@@ -1,7 +1,7 @@
 # This file is a part of Julia. License is MIT: https://julialang.org/license
 
 catcmd = `cat`
-if is_windows()
+if Sys.iswindows()
     try # use busybox-w32 on windows
         success(`busybox`)
         catcmd = `busybox cat`
@@ -257,7 +257,7 @@ let exename = `$(Base.julia_cmd()) --precompiled=yes --startup-file=no`
             """)
         cp(testfile, joinpath(dir, ".juliarc.jl"))
 
-        withenv((is_windows() ? "USERPROFILE" : "HOME") => dir) do
+        withenv((Sys.iswindows() ? "USERPROFILE" : "HOME") => dir) do
             output = "String[\"foo\", \"-bar\", \"--baz\"]"
             @test readchomp(`$exename $testfile foo -bar --baz`) == output
             @test readchomp(`$exename $testfile -- foo -bar --baz`) == output
@@ -295,7 +295,7 @@ let exename = `$(Base.julia_cmd()) --precompiled=yes --startup-file=no`
 
         readsplit(cmd) = split(readchomp(cmd), '\n')
 
-        withenv((is_windows() ? "USERPROFILE" : "HOME") => dir) do
+        withenv((Sys.iswindows() ? "USERPROFILE" : "HOME") => dir) do
             @test readsplit(`$exename $a`) ==
                 [a, a,
                  b, a]
@@ -342,7 +342,7 @@ let exename = `$(Base.julia_cmd()) --precompiled=yes --startup-file=no`
     # issue #12671, starting from a non-directory
     # rm(dir) fails on windows with Permission denied
     # and was an upstream bug in llvm <= v3.3
-    if !is_windows() && Base.libllvm_version > v"3.3"
+    if !Sys.iswindows() && Base.libllvm_version > v"3.3"
         testdir = mktempdir()
         cd(testdir) do
             rm(testdir)
diff --git a/test/compile.jl b/test/compile.jl
index c4d2f5353cafe..8821493033395 100644
--- a/test/compile.jl
+++ b/test/compile.jl
@@ -286,7 +286,7 @@ try
     @test !isdefined(Main, :FooBar1)
 
     relFooBar_file = joinpath(dir, "subfolder", "..", "FooBar.jl")
-    @test Base.stale_cachefile(relFooBar_file, joinpath(dir, "FooBar.ji")) == !is_windows() # `..` is not a symlink on Windows
+    @test Base.stale_cachefile(relFooBar_file, joinpath(dir, "FooBar.ji")) == !Sys.iswindows() # `..` is not a symlink on Windows
     mkdir(joinpath(dir, "subfolder"))
     @test !Base.stale_cachefile(relFooBar_file, joinpath(dir, "FooBar.ji"))
 
diff --git a/test/core.jl b/test/core.jl
index a1df02b58b57d..1051cef84ea0d 100644
--- a/test/core.jl
+++ b/test/core.jl
@@ -2149,7 +2149,7 @@ let x = [1,2,3]
 end
 
 # sig 2 is SIGINT per the POSIX.1-1990 standard
-if !is_windows()
+if !Sys.iswindows()
     ccall(:jl_exit_on_sigint, Void, (Cint,), 0)
     @test_throws InterruptException begin
         ccall(:kill, Void, (Cint, Cint,), getpid(), 2)
diff --git a/test/dates/conversions.jl b/test/dates/conversions.jl
index d092ec6749fc6..a043b95f4dcc6 100644
--- a/test/dates/conversions.jl
+++ b/test/dates/conversions.jl
@@ -48,7 +48,7 @@
 @test typeof(Dates.today()) <: Dates.Date
 @test typeof(Dates.now(Dates.UTC)) <: Dates.DateTime
 
-if is_apple()
+if Sys.isapple()
     withenv("TZ" => "UTC") do
         @test abs(Dates.now() - now(Dates.UTC)) < Dates.Second(1)
     end
diff --git a/test/distributed_exec.jl b/test/distributed_exec.jl
index 052323beb85d7..47b46b788a740 100644
--- a/test/distributed_exec.jl
+++ b/test/distributed_exec.jl
@@ -270,7 +270,7 @@ test_indexing(RemoteChannel(id_other))
 
 dims = (20,20,20)
 
-if is_linux()
+if Sys.islinux()
     S = SharedArray{Int64,3}(dims)
     @test startswith(S.segname, "/jl")
     @test !ispath("/dev/shm" * S.segname)
@@ -962,7 +962,7 @@ if DoFullTest
     @test workers() == all_w
     @test all([p == remotecall_fetch(myid, p) for p in all_w])
 
-if is_unix() # aka have ssh
+if Sys.isunix() # aka have ssh
     function test_n_remove_pids(new_pids)
         for p in new_pids
             w_in_remote = sort(remotecall_fetch(workers, p))
@@ -1233,7 +1233,7 @@ const get_num_threads = function() # anonymous so it will be serialized when cal
         end
 
         # OSX BLAS looks at an environment variable
-        if is_apple()
+        if Sys.isapple()
             return ENV["VECLIB_MAXIMUM_THREADS"]
         end
     end
diff --git a/test/examples.jl b/test/examples.jl
index fd63c59f460cd..c406c5784ca5e 100644
--- a/test/examples.jl
+++ b/test/examples.jl
@@ -37,7 +37,7 @@ include(joinpath(dir, "queens.jl"))
 # Different cluster managers do not play well together. Since
 # the test infrastructure already uses LocalManager, we will test the simple
 # cluster manager example through a new Julia session.
-if is_unix()
+if Sys.isunix()
     script = joinpath(dir, "clustermanager/simple/test_simple.jl")
     cmd = `$(Base.julia_cmd()) --startup-file=no $script`
     if !success(pipeline(cmd; stdout=STDOUT, stderr=STDERR)) && ccall(:jl_running_on_valgrind,Cint,()) == 0
diff --git a/test/file.jl b/test/file.jl
index 269d5fe2ae9cd..527fadcbaa7e6 100644
--- a/test/file.jl
+++ b/test/file.jl
@@ -26,7 +26,7 @@ let err = nothing
     end
 end
 
-if !is_windows() || Sys.windows_version() >= Sys.WINDOWS_VISTA_VER
+if !Sys.iswindows() || Sys.windows_version() >= Sys.WINDOWS_VISTA_VER
     dirlink = joinpath(dir, "dirlink")
     symlink(subdir, dirlink)
     # relative link
@@ -37,7 +37,7 @@ if !is_windows() || Sys.windows_version() >= Sys.WINDOWS_VISTA_VER
     cd(pwd_)
 end
 
-if !is_windows()
+if !Sys.iswindows()
     link = joinpath(dir, "afilelink.txt")
     symlink(file, link)
     # relative link
@@ -67,7 +67,7 @@ chmod(file, filemode(file) | 0o222)
 @test filemode(file) & 0o111 == 0
 @test filesize(file) == 0
 
-if is_windows()
+if Sys.iswindows()
     permissions = 0o444
     @test filemode(dir) & 0o777 != permissions
     @test filemode(subdir) & 0o777 != permissions
@@ -103,7 +103,7 @@ end
 
 # On windows the filesize of a folder is the accumulation of all the contained
 # files and is thus zero in this case.
-if is_windows()
+if Sys.iswindows()
     @test filesize(dir) == 0
 else
     @test filesize(dir) > 0
@@ -118,15 +118,15 @@ end
 #@test Int(time()) >= Int(mtime(file)) >= Int(mtime(dir)) >= 0 # 1 second accuracy should be sufficient
 
 # test links
-if is_unix()
+if Sys.isunix()
     @test islink(link) == true
     @test readlink(link) == file
 end
 
-if !is_windows() || Sys.windows_version() >= Sys.WINDOWS_VISTA_VER
+if !Sys.iswindows() || Sys.windows_version() >= Sys.WINDOWS_VISTA_VER
     @test islink(dirlink) == true
     @test isdir(dirlink) == true
-    @test readlink(dirlink) == subdir * (is_windows() ? "\\" : "")
+    @test readlink(dirlink) == subdir * (Sys.iswindows() ? "\\" : "")
 end
 
 # rm recursive TODO add links
@@ -162,7 +162,7 @@ rm(c_tmpdir, recursive=true)
 @test_throws Base.UVError rm(c_tmpdir, recursive=true)
 @test rm(c_tmpdir, force=true, recursive=true) === nothing
 
-if !is_windows()
+if !Sys.iswindows()
     # chown will give an error if the user does not have permissions to change files
     if get(ENV, "USER", "") == "root" || get(ENV, "HOME", "") == "/root"
         chown(file, -2, -1)  # Change the file owner to nobody
@@ -236,7 +236,7 @@ function test_monitor_wait(tval)
     end
     fname, events = wait(fm)
     close(fm)
-    if is_linux() || is_windows() || is_apple()
+    if Sys.islinux() || Sys.iswindows() || Sys.isapple()
         @test fname == basename(file)
     else
         @test fname == ""  # platforms where F_GETPATH is not available
@@ -307,7 +307,7 @@ my_tempdir = tempdir()
 
 path = tempname()
 # Issue #9053.
-@test ispath(path) == is_windows()
+@test ispath(path) == Sys.iswindows()
 ispath(path) && rm(path)
 
 (p, f) = mktemp()
@@ -476,7 +476,7 @@ end
 
 # issue #10506 #10434
 ## Tests for directories and links to directories
-if !is_windows() || Sys.windows_version() >= Sys.WINDOWS_VISTA_VER
+if !Sys.iswindows() || Sys.windows_version() >= Sys.WINDOWS_VISTA_VER
     function setup_dirs(tmpdir)
         srcdir = joinpath(tmpdir, "src")
         hidden_srcdir = joinpath(tmpdir, ".hidden_srcdir")
@@ -686,7 +686,7 @@ end
 
 # issue #10506 #10434
 ## Tests for files and links to files as well as directories and links to directories
-if !is_windows()
+if !Sys.iswindows()
     function setup_files(tmpdir)
         srcfile = joinpath(tmpdir, "srcfile.txt")
         hidden_srcfile = joinpath(tmpdir, ".hidden_srcfile.txt")
@@ -918,7 +918,7 @@ let f = open(file, "w")
     f = open(file, "r")
     test_LibcFILE(convert(Libc.FILE, f))
     close(f)
-    if is_windows()
+    if Sys.iswindows()
         f = RawFD(ccall(:_open, Cint, (Cstring, Cint), file, Base.Filesystem.JL_O_RDONLY))
     else
         f = RawFD(ccall(:open, Cint, (Cstring, Cint), file, Base.Filesystem.JL_O_RDONLY))
@@ -937,7 +937,7 @@ end
 @test_throws ArgumentError open("ba\0d", "w")
 @test_throws ArgumentError cp(file, "ba\0d")
 @test_throws ArgumentError mv(file, "ba\0d")
-if !is_windows() || (Sys.windows_version() >= Sys.WINDOWS_VISTA_VER)
+if !Sys.iswindows() || (Sys.windows_version() >= Sys.WINDOWS_VISTA_VER)
     @test_throws ArgumentError symlink(file, "ba\0d")
 else
     @test_throws ErrorException symlink(file, "ba\0d")
@@ -959,7 +959,7 @@ cd(dirwalk) do
         touch(joinpath("sub_dir1", "file$i"))
     end
     touch(joinpath("sub_dir2", "file_dir2"))
-    has_symlinks = !is_windows() || (Sys.windows_version() >= Sys.WINDOWS_VISTA_VER)
+    has_symlinks = !Sys.iswindows() || (Sys.windows_version() >= Sys.WINDOWS_VISTA_VER)
     follow_symlink_vec = has_symlinks ? [true, false] : [false]
     has_symlinks && symlink(abspath("sub_dir2"), joinpath("sub_dir1", "link"))
     for follow_symlinks in follow_symlink_vec
@@ -1048,11 +1048,11 @@ rm(dirwalk, recursive=true)
 ############
 # Clean up #
 ############
-if !is_windows()
+if !Sys.iswindows()
     rm(link)
     rm(rellink)
 end
-if !is_windows() || (Sys.windows_version() >= Sys.WINDOWS_VISTA_VER)
+if !Sys.iswindows() || (Sys.windows_version() >= Sys.WINDOWS_VISTA_VER)
     rm(dirlink)
     rm(relsubdirlink)
 end
@@ -1113,7 +1113,7 @@ test2_12992()
 test2_12992()
 
 # issue 13559
-if !is_windows()
+if !Sys.iswindows()
 function test_13559()
     fn = tempname()
     run(`mkfifo $fn`)
diff --git a/test/libdl.jl b/test/libdl.jl
index 4aba53527335c..d283bc15cac18 100644
--- a/test/libdl.jl
+++ b/test/libdl.jl
@@ -5,7 +5,7 @@
 dlls = Libdl.dllist()
 @test !isempty(dlls)
 @test length(dlls) > 3 # at a bare minimum, probably have some version of libstdc, libgcc, libjulia, ...
-if !is_windows() || Sys.windows_version() >= Sys.WINDOWS_VISTA_VER
+if !Sys.iswindows() || Sys.windows_version() >= Sys.WINDOWS_VISTA_VER
     for dl in dlls
         if isfile(dl) && (Libdl.dlopen_e(dl) != C_NULL)
             @test Base.samefile(Libdl.dlpath(dl), dl)
diff --git a/test/libgit2.jl b/test/libgit2.jl
index f0de7c7262fe8..34c4698866f0d 100644
--- a/test/libgit2.jl
+++ b/test/libgit2.jl
@@ -100,7 +100,7 @@ end
 end
 
 # See #21872 and #21636
-LibGit2.version() >= v"0.26.0" && is_unix() && @testset "Default config with symlink" begin
+LibGit2.version() >= v"0.26.0" && Sys.isunix() && @testset "Default config with symlink" begin
     with_libgit2_temp_home() do tmphome
         write(joinpath(tmphome, "real_gitconfig"), "[fake]\n\tproperty = BBB")
         symlink(joinpath(tmphome, "real_gitconfig"),
@@ -1430,7 +1430,7 @@ mktempdir() do dir
     end
 
 
-    if is_unix()
+    if Sys.isunix()
         @testset "checkout/proptest" begin
             repo = LibGit2.GitRepo(test_repo)
             try
@@ -1483,7 +1483,7 @@ mktempdir() do dir
     # The following tests require that we can fake a TTY so that we can provide passwords
     # which use the `getpass` function. At the moment we can only fake this on UNIX based
     # systems.
-    if is_unix()
+    if Sys.isunix()
         @testset "SSH credential prompt" begin
             url = "git@github.com/test/package.jl"
 
@@ -1645,7 +1645,7 @@ mktempdir() do dir
     @testset "SSH" begin
         sshd_command = ""
         ssh_repo = joinpath(dir, "Example.SSH")
-        if !is_windows()
+        if !Sys.iswindows()
             try
                 # SSHD needs to be executed by its full absolute path
                 sshd_command = strip(readstring(`which sshd`))
@@ -1695,7 +1695,7 @@ mktempdir() do dir
                     sshp = spawn_sshd()
 
                     TIOCSCTTY_str = "ccall(:ioctl, Void, (Cint, Cint, Int64), 0,
-                        (is_bsd() || is_apple()) ? 0x20007461 : is_linux() ? 0x540E :
+                        (Sys.isbsd() || Sys.isapple()) ? 0x20007461 : Sys.islinux() ? 0x540E :
                         error(\"Fill in TIOCSCTTY for this OS here\"), 0)"
 
                     # To fail rather than hang
@@ -1821,7 +1821,7 @@ mktempdir() do dir
     @testset "Hostname verification" begin
         openssl_installed = false
         common_name = ""
-        if is_linux()
+        if Sys.islinux()
             try
                 # OpenSSL needs to be on the path
                 openssl_installed = !isempty(readstring(`openssl version`))
diff --git a/test/misc.jl b/test/misc.jl
index 3063912756061..cd192a15cfbd9 100644
--- a/test/misc.jl
+++ b/test/misc.jl
@@ -507,7 +507,7 @@ let s = "abcα🐨\0x\0"
 end
 
 # clipboard functionality
-if is_windows()
+if Sys.iswindows()
     for str in ("Hello, world.", "∀ x ∃ y", "")
         clipboard(str)
         @test clipboard() == str
@@ -546,7 +546,7 @@ let creds = Base.LibGit2.CachedCredentials()
 end
 
 # Test that we can VirtualProtect jitted code to writable
-if is_windows()
+if Sys.iswindows()
     @noinline function WeVirtualProtectThisToRWX(x, y)
         x+y
     end
diff --git a/test/osutils.jl b/test/osutils.jl
index b84688f55609b..9d7783e9ec03f 100644
--- a/test/osutils.jl
+++ b/test/osutils.jl
@@ -1,18 +1,18 @@
 # This file is a part of Julia. License is MIT: https://julialang.org/license
 
-@test !Base.is_unix(:Windows)
-@test !Base.is_linux(:Windows)
-@test Base.is_linux(:Linux)
-@test Base.is_windows(:Windows)
-@test Base.is_windows(:NT)
-@test !Base.is_windows(:Darwin)
-@test Base.is_apple(:Darwin)
-@test Base.is_apple(:Apple)
-@test !Base.is_apple(:Windows)
-@test Base.is_unix(:Darwin)
-@test Base.is_unix(:FreeBSD)
-@test_throws ArgumentError Base.is_unix(:BeOS)
-if !is_windows()
+@test !Sys.isunix(:Windows)
+@test !Sys.islinux(:Windows)
+@test Sys.islinux(:Linux)
+@test Sys.iswindows(:Windows)
+@test Sys.iswindows(:NT)
+@test !Sys.iswindows(:Darwin)
+@test Sys.isapple(:Darwin)
+@test Sys.isapple(:Apple)
+@test !Sys.isapple(:Windows)
+@test Sys.isunix(:Darwin)
+@test Sys.isunix(:FreeBSD)
+@test_throws ArgumentError Sys.isunix(:BeOS)
+if !Sys.iswindows()
     @test Sys.windows_version() == v"0.0.0"
 else
     @test Sys.windows_version() >= v"1.0.0-"
diff --git a/test/path.jl b/test/path.jl
index e02176c33945f..3a27bcb271ab6 100644
--- a/test/path.jl
+++ b/test/path.jl
@@ -11,7 +11,7 @@ for S in (String, GenericString)
     @test dirname(S("foo$(sep)bar")) == "foo"
 
     @test expanduser(S("x")) == "x"
-    @test expanduser(S("~")) == (is_windows() ? "~" : homedir())
+    @test expanduser(S("~")) == (Sys.iswindows() ? "~" : homedir())
 
     @test isabspath(S(homedir()))
     @test !isabspath(S("foo"))
@@ -68,7 +68,7 @@ for S in (String, GenericString)
     @test joinpath(splitdir(S(homedir()))...) == homedir()
     @test string(splitdrive(S(homedir()))...) == homedir()
 
-    if is_windows()
+    if Sys.iswindows()
         @test splitdrive(S("\\\\servername\\hello.world\\filename.ext")) ==
             ("\\\\servername\\hello.world","\\filename.ext")
         @test splitdrive(S("\\\\servername.com\\hello.world\\filename.ext")) ==
@@ -95,8 +95,8 @@ end
 
 @test isabspath("~") == false
 @test isabspath("/") == true # on windows, this is relatively absolute
-@test isabspath("A:/") == is_windows()
-@test isabspath("B:\\") == is_windows()
+@test isabspath("A:/") == Sys.iswindows()
+@test isabspath("B:\\") == Sys.iswindows()
 @test isabspath("./") == false
 @test isabspath("C:") == false
 @test isabspath("C:.") == false
@@ -104,8 +104,8 @@ end
 @test isabspath(".:/") == false
 #@test isabspath("_:/") == false # FIXME?
 #@test isabspath("AB:/") == false # FIXME?
-@test isabspath("\\\\") == is_windows()
-if is_unix()
+@test isabspath("\\\\") == Sys.iswindows()
+if Sys.isunix()
     @test isabspath(expanduser("~")) == true
     @test startswith(expanduser("~"), homedir())
 else
@@ -199,8 +199,8 @@ test_relpath()
 @test isa(joinpath(abspath("a"), "b"), String)
 
 # homedir
-let var = is_windows() ? "USERPROFILE" : "HOME",
-    MAX_PATH = is_windows() ? 240 : 1020
+let var = Sys.iswindows() ? "USERPROFILE" : "HOME",
+    MAX_PATH = Sys.iswindows() ? 240 : 1020
     for i = 0:9
         local home = " "^MAX_PATH * "123456789"[1:i]
         @test withenv(var => home) do
diff --git a/test/perf/micro/perf.jl b/test/perf/micro/perf.jl
index e5686d98d079d..c688694363741 100644
--- a/test/perf/micro/perf.jl
+++ b/test/perf/micro/perf.jl
@@ -138,7 +138,7 @@ end
 
 ## printfd ##
 
-if is_unix()
+if Sys.isunix()
     function printfd(n)
         open("/dev/null", "w") do io
             for i = 1:n
diff --git a/test/perf/perfutil.jl b/test/perf/perfutil.jl
index 7e0ddf8cbc072..85c9ee89b46a6 100644
--- a/test/perf/perfutil.jl
+++ b/test/perf/perfutil.jl
@@ -102,7 +102,7 @@ end
 
 function maxrss(name)
     # FIXME: call uv_getrusage instead here
-    @static if is_linux()
+    @static if Sys.islinux()
         rus = Array{Int64}(div(144,8))
         fill!(rus, 0x0)
         res = ccall(:getrusage, Int32, (Int32, Ptr{Void}), 0, rus)
diff --git a/test/pkg.jl b/test/pkg.jl
index abd04ea9d59f7..d2c11e7f61ac5 100644
--- a/test/pkg.jl
+++ b/test/pkg.jl
@@ -322,7 +322,7 @@ temp_pkg_dir() do
         include(Pkg.dir("Example","src","Example.jl"))
         meth = first(methods(Example.domath))
         fname = string(meth.file)
-        @test ('\\' in fname) == is_windows()
+        @test ('\\' in fname) == Sys.iswindows()
         @test startswith(Base.url(meth), "https://github.com/JuliaLang/Example.jl/tree")
     end
 
@@ -556,7 +556,7 @@ temp_pkg_dir() do
         mkdir(home)
         write(joinpath(home, ".juliarc.jl"), "const JULIA_RC_LOADED = true")
 
-        withenv((is_windows() ? "USERPROFILE" : "HOME") => home) do
+        withenv((Sys.iswindows() ? "USERPROFILE" : "HOME") => home) do
             code = "redirect_stderr(STDOUT); Pkg.build(\"$package\")"
 
             msg = readstring(`$(Base.julia_cmd()) --startup-file=no -e $code`)
diff --git a/test/pollfd.jl b/test/pollfd.jl
index 0218ac8fc104c..fdc44439c1d51 100644
--- a/test/pollfd.jl
+++ b/test/pollfd.jl
@@ -13,7 +13,7 @@ intvls = [2, .2, .1, .005]
 
 pipe_fds = Vector{Any}(n)
 for i in 1:n
-    @static if is_windows()
+    @static if Sys.iswindows()
         pipe_fds[i] = Array{Libc.WindowsRawSocket}(2)
         0 == ccall(:wsasocketpair, Cint, (Cint, Cuint, Cint, Ptr{Libc.WindowsRawSocket}), 1, 1, 6, pipe_fds[i]) || error(Libc.FormatMessage())
     else
@@ -41,7 +41,7 @@ function pfd_tst_reads(idx, intvl)
     # @test t_elapsed <= (intvl + 1)
 
     dout = Array{UInt8}(1)
-    @static if is_windows()
+    @static if Sys.iswindows()
         1 == ccall(:recv, stdcall, Cint, (Ptr{Void}, Ptr{UInt8}, Cint, Cint), pipe_fds[idx][1], dout, 1, 0) || error(Libc.FormatMessage())
     else
         @test 1 == ccall(:read, Csize_t, (Cint, Ptr{UInt8}, Csize_t), pipe_fds[idx][1], dout, 1)
@@ -96,7 +96,7 @@ for (i, intvl) in enumerate(intvls)
             @test event.writable
 
             if isodd(idx)
-                @static if is_windows()
+                @static if Sys.iswindows()
                     1 == ccall(:send, stdcall, Cint, (Ptr{Void}, Ptr{UInt8}, Cint, Cint), pipe_fds[idx][2], "A", 1, 0) || error(Libc.FormatMessage())
                 else
                     @test 1 == ccall(:write, Csize_t, (Cint, Ptr{UInt8}, Csize_t), pipe_fds[idx][2], "A", 1)
@@ -112,7 +112,7 @@ end
 
 for i in 1:n
     for j = 1:2
-        @static if is_windows()
+        @static if Sys.iswindows()
             0 == ccall(:closesocket, stdcall, Cint, (Ptr{Void},), pipe_fds[i][j]) || error(Libc.FormatMessage())
         else
             @test 0 == ccall(:close, Cint, (Cint,), pipe_fds[i][j])
diff --git a/test/read.jl b/test/read.jl
index 6f794a84f59bd..5b9be4215c854 100644
--- a/test/read.jl
+++ b/test/read.jl
@@ -83,7 +83,7 @@ push!(l, ("TCPSocket", io))
 io = (text) -> begin
     a = "\\\\.\\pipe\\uv-test-$(randstring(6))"
     b = joinpath(dir, "socket-$(randstring(6))")
-    socketname = is_windows() ? a : b
+    socketname = Sys.iswindows() ? a : b
     srv = listen(socketname)
     run_test_server(srv, text)
     connect(socketname)
@@ -98,7 +98,7 @@ push!(l, ("PipeEndpoint", io))
 #FIXME See https://github.com/JuliaLang/julia/issues/14747
 #      Reading from open(::Command) seems to deadlock on Linux/Travis
 #=
-if !is_windows()
+if !Sys.iswindows()
 
 # Windows type command not working?
 # See "could not spawn `type 'C:\Users\appveyor\AppData\Local\Temp\1\jul3516.tmp\file.txt'`"
@@ -107,7 +107,7 @@ if !is_windows()
 # Pipe
 io = (text) -> begin
     write(filename, text)
-    open(`$(is_windows() ? "type" : "cat") $filename`)[1]
+    open(`$(Sys.iswindows() ? "type" : "cat") $filename`)[1]
 #    Was open(`echo -n $text`)[1]
 #    See https://github.com/JuliaLang/julia/issues/14747
 end
@@ -415,13 +415,13 @@ rm(f)
 io = Base.Filesystem.open(f, Base.Filesystem.JL_O_WRONLY | Base.Filesystem.JL_O_CREAT | Base.Filesystem.JL_O_EXCL, 0o000)
 @test write(io, "abc") == 3
 close(io)
-if !is_windows() && get(ENV, "USER", "") != "root" && get(ENV, "HOME", "") != "/root"
+if !Sys.iswindows() && get(ENV, "USER", "") != "root" && get(ENV, "HOME", "") != "/root"
     # msvcrt _wchmod documentation states that all files are readable,
     # so we don't test that it correctly set the umask on windows
     @test_throws SystemError open(f)
     @test_throws Base.UVError Base.Filesystem.open(f, Base.Filesystem.JL_O_RDONLY)
 else
-    is_windows() || warn("file permissions tests skipped due to running tests as root (not recommended)")
+    Sys.iswindows() || warn("file permissions tests skipped due to running tests as root (not recommended)")
     close(open(f))
 end
 chmod(f, 0o400)
diff --git a/test/reflection.jl b/test/reflection.jl
index 5a85bb31c729f..3d9a2c2976475 100644
--- a/test/reflection.jl
+++ b/test/reflection.jl
@@ -546,7 +546,7 @@ function has_backslashes(meth::Method)
 end
 has_backslashes(x) = Nullable{Method}()
 h16850 = has_backslashes(Base)
-if is_windows()
+if Sys.iswindows()
     if isnull(h16850)
         warn("No methods found in Base with backslashes in file name, ",
              "skipping test for Base.url")
diff --git a/test/repl.jl b/test/repl.jl
index 935a48ea2c2dc..321a9434f0afb 100644
--- a/test/repl.jl
+++ b/test/repl.jl
@@ -31,7 +31,7 @@ ccall(:jl_exit_on_sigint, Void, (Cint,), 0)
 # in the mix. If verification needs to be done, keep it to the bare minimum. Basically
 # this should make sure nothing crashes without depending on how exactly the control
 # characters are being used.
-if !is_windows() || Sys.windows_version() >= Sys.WINDOWS_VISTA_VER
+if !Sys.iswindows() || Sys.windows_version() >= Sys.WINDOWS_VISTA_VER
     stdin_write, stdout_read, stderr_read, repl = fake_repl()
 
     repl.specialdisplay = Base.REPL.REPLDisplay(repl)
@@ -100,7 +100,7 @@ if !is_windows() || Sys.windows_version() >= Sys.WINDOWS_VISTA_VER
     cd(origpwd)
 
     # issue #20482
-    if !is_windows()
+    if !Sys.iswindows()
         write(stdin_write, ";")
         readuntil(stdout_read, "shell> ")
         write(stdin_write, "echo hello >/dev/null\n")
@@ -126,7 +126,7 @@ if !is_windows() || Sys.windows_version() >= Sys.WINDOWS_VISTA_VER
 
     # issues #22176 & #20482
     # TODO: figure out how to test this on Windows
-    is_windows() || let tmp = tempname()
+    Sys.iswindows() || let tmp = tempname()
         try
             write(stdin_write, ";")
             readuntil(stdout_read, "shell> ")
@@ -534,7 +534,7 @@ begin
 end
 
 # Simple non-standard REPL tests
-if !is_windows() || Sys.windows_version() >= Sys.WINDOWS_VISTA_VER
+if !Sys.iswindows() || Sys.windows_version() >= Sys.WINDOWS_VISTA_VER
     stdin_write, stdout_read, stdout_read, repl = fake_repl()
     panel = LineEdit.Prompt("testπ";
         prompt_prefix="\e[38;5;166m",
@@ -579,7 +579,7 @@ ccall(:jl_exit_on_sigint, Void, (Cint,), 1)
 let exename = Base.julia_cmd()
 
 # Test REPL in dumb mode
-if !is_windows()
+if !Sys.iswindows()
     TestHelpers.with_fake_pty() do slave, master
         nENV = copy(ENV)
         nENV["TERM"] = "dumb"
@@ -600,7 +600,7 @@ if !is_windows()
 end
 
 # Test stream mode
-if !is_windows() || Sys.windows_version() >= Sys.WINDOWS_VISTA_VER
+if !Sys.iswindows() || Sys.windows_version() >= Sys.WINDOWS_VISTA_VER
     outs, ins, p = readandwrite(`$exename --startup-file=no --quiet`)
     write(ins,"1\nquit()\n")
     @test readstring(outs) == "1\n"
diff --git a/test/replcompletions.jl b/test/replcompletions.jl
index d741ad06d8761..fd53878cac705 100644
--- a/test/replcompletions.jl
+++ b/test/replcompletions.jl
@@ -471,7 +471,7 @@ c, r, res = test_scomplete(s)
 # which would raise an error in the repl code.
 @test (String[], 0:-1, false) == test_scomplete("\$a")
 
-if is_unix()
+if Sys.isunix()
     #Assume that we can rely on the existence and accessibility of /tmp
 
     # Tests path in Julia code and closing " if it's a file
@@ -622,12 +622,12 @@ let #test that it can auto complete with spaces in file/path
     mkdir(dir)
     cd(path) do
         open(joinpath(space_folder, "space .file"),"w") do f
-            s = is_windows() ? "rm $dir_space\\\\space" : "cd $dir_space/space"
+            s = Sys.iswindows() ? "rm $dir_space\\\\space" : "cd $dir_space/space"
             c,r = test_scomplete(s)
             @test r == endof(s)-4:endof(s)
             @test "space\\ .file" in c
 
-            s = is_windows() ? "cd(\"β $dir_space\\\\space" : "cd(\"β $dir_space/space"
+            s = Sys.iswindows() ? "cd(\"β $dir_space\\\\space" : "cd(\"β $dir_space/space"
             c,r = test_complete(s)
             @test r == endof(s)-4:endof(s)
             @test "space\\ .file\"" in c
@@ -645,7 +645,7 @@ end
 c,r = test_complete("cd(\"folder_do_not_exist_77/file")
 @test length(c) == 0
 
-if is_windows()
+if Sys.iswindows()
     tmp = tempname()
     path = dirname(tmp)
     file = basename(tmp)
diff --git a/test/show.jl b/test/show.jl
index ff4d5ac4bf850..02dc18470cdae 100644
--- a/test/show.jl
+++ b/test/show.jl
@@ -372,7 +372,7 @@ let oldout = STDOUT, olderr = STDERR
         @test wrerr === STDERR
         err = @async readstring(rderr)
         @test dump(Int64) === nothing
-        if !is_windows()
+        if !Sys.iswindows()
             close(wrout)
             close(wrerr)
         end
diff --git a/test/socket.jl b/test/socket.jl
index 917d3c240a13c..8af9c7b86e93f 100644
--- a/test/socket.jl
+++ b/test/socket.jl
@@ -94,7 +94,7 @@ for testport in [0, defaultport]
 end
 
 mktempdir() do tmpdir
-    socketname = is_windows() ? ("\\\\.\\pipe\\uv-test-" * randstring(6)) : joinpath(tmpdir, "socket")
+    socketname = Sys.iswindows() ? ("\\\\.\\pipe\\uv-test-" * randstring(6)) : joinpath(tmpdir, "socket")
     c = Base.Condition()
     tsk = @async begin
         s = listen(socketname)
@@ -176,7 +176,7 @@ begin
     close(a)
     close(b)
 end
-if !is_windows() || Sys.windows_version() >= Sys.WINDOWS_VISTA_VER
+if !Sys.iswindows() || Sys.windows_version() >= Sys.WINDOWS_VISTA_VER
     a = UDPSocket()
     b = UDPSocket()
     bind(a, ip"::1", UInt16(port))
@@ -227,7 +227,7 @@ end
 # Local-machine broadcast
 let
     # (Mac OS X's loopback interface doesn't support broadcasts)
-    bcastdst = is_apple() ? ip"255.255.255.255" : ip"127.255.255.255"
+    bcastdst = Sys.isapple() ? ip"255.255.255.255" : ip"127.255.255.255"
 
     function create_socket()
         s = UDPSocket()
@@ -251,7 +251,7 @@ let
     try
         # bsd family do not allow broadcasting to ip"255.255.255.255"
         # or ip"127.255.255.255"
-        @static if !is_bsd() || is_apple()
+        @static if !Sys.isbsd() || Sys.isapple()
             send(c, bcastdst, 2000, "hello")
             recvs = [@async @test String(recv(s)) == "hello" for s in (a, b)]
             wait_with_timeout(recvs)
@@ -288,12 +288,12 @@ let P = Pipe()
     # on windows, the kernel fails to do even that
     # causing the `write` call to freeze
     # so we end up forced to do a slightly weaker test here
-    is_windows() || wait(t)
+    Sys.iswindows() || wait(t)
     @test isopen(P) # without an active uv_reader, P shouldn't be closed yet
     @test !eof(P) # should already know this,
     @test isopen(P) #  so it still shouldn't have an active uv_reader
     @test readuntil(P, 'w') == "llow"
-    is_windows() && wait(t)
+    Sys.iswindows() && wait(t)
     @test eof(P)
     @test !isopen(P) # eof test should have closed this by now
     close(P) # should be a no-op, just make sure
diff --git a/test/spawn.jl b/test/spawn.jl
index 1a2bfaffabb8f..f053b5c4bb95a 100644
--- a/test/spawn.jl
+++ b/test/spawn.jl
@@ -16,7 +16,7 @@ catcmd = `cat`
 shcmd = `sh`
 sleepcmd = `sleep`
 lscmd = `ls`
-if is_windows()
+if Sys.iswindows()
     try # use busybox-w32 on windows
         success(`busybox`)
         yescmd = `busybox yes`
@@ -46,7 +46,7 @@ out = readstring(`$echocmd hello` & `$echocmd world`)
 @test (run(`$printfcmd "       \033[34m[stdio passthrough ok]\033[0m\n"`); true)
 
 # Test for SIGPIPE being treated as normal termination (throws an error if broken)
-is_unix() && run(pipeline(yescmd, `head`, DevNull))
+Sys.isunix() && run(pipeline(yescmd, `head`, DevNull))
 
 begin
     a = Base.Condition()
@@ -65,7 +65,7 @@ if valgrind_off
     @test_throws Base.UVError run(`foo_is_not_a_valid_command`)
 end
 
-if is_unix()
+if Sys.isunix()
     prefixer(prefix, sleep) = `sh -c "while IFS= read REPLY; do echo '$prefix ' \$REPLY; sleep $sleep; done"`
     @test success(pipeline(`sh -c "for i in 1 2 3 4 5 6 7 8 9 10; do echo \$i; sleep 0.1; done"`,
                        prefixer("A", 0.2) & prefixer("B", 0.2)))
@@ -93,7 +93,7 @@ let file = tempname()
 end
 
 # Stream Redirection
-if !is_windows() # WINNT reports operation not supported on socket (ENOTSUP) for this test
+if !Sys.iswindows() # WINNT reports operation not supported on socket (ENOTSUP) for this test
     local r = Channel(1)
     local port, server, sock, client, t1, t2
     t1 = @async begin
@@ -121,7 +121,7 @@ end
        readstring(`$shcmd -c "echo \$TEST"`); end) == "Hello World\n"
 let pathA = readchomp(setenv(`$shcmd -c "pwd -P"`;dir="..")),
     pathB = readchomp(setenv(`$shcmd -c "cd .. && pwd -P"`))
-    if is_windows()
+    if Sys.iswindows()
         # on windows, sh returns posix-style paths that are not valid according to ispath
         @test pathA == pathB
     else
@@ -298,11 +298,11 @@ let out = Pipe(), echo = `$exename --startup-file=no -e 'print(STDOUT, " 1\t", r
         @test iswritable(out)
         close(out.in)
         @test !isopen(out.in)
-        is_windows() || @test !isopen(out.out) # it takes longer to propagate EOF through the Windows event system
+        Sys.iswindows() || @test !isopen(out.out) # it takes longer to propagate EOF through the Windows event system
         @test_throws ArgumentError write(out, "now closed error")
         @test isreadable(out)
         @test !iswritable(out)
-        if is_windows()
+        if Sys.iswindows()
             # WINNT kernel does not provide a fast mechanism for async propagation
             # of EOF for a blocking stream, so just wait for it to catch up.
             # This shouldn't take much more than 32ms.
@@ -341,7 +341,7 @@ let fname = tempname()
     write(fname, "test\n")
     code = """
     cmd = pipeline(`echo asdf`,`cat`)
-    if is_windows()
+    if Sys.iswindows()
         try
             success(`busybox`)
             cmd = pipeline(`busybox echo asdf`,`busybox cat`)
@@ -383,7 +383,7 @@ end
 @test_throws ErrorException collect(eachline(pipeline(`$catcmd _doesnt_exist__111_`, stderr=DevNull)))
 
 # make sure windows_verbatim strips quotes
-if is_windows()
+if Sys.iswindows()
     readstring(`cmd.exe /c dir /b spawn.jl`) == readstring(Cmd(`cmd.exe /c dir /b "\"spawn.jl\""`, windows_verbatim=true))
 end
 
@@ -422,7 +422,7 @@ end
 @test reduce(&, [`$echocmd abc`, `$echocmd def`, `$echocmd hij`]) == `$echocmd abc` & `$echocmd def` & `$echocmd hij`
 
 # test for proper handling of FD exhaustion
-if is_unix()
+if Sys.isunix()
     let ps = Pipe[]
         ulimit_n = tryparse(Int, readchomp(`sh -c 'ulimit -n'`))
         try
diff --git a/test/strings/basic.jl b/test/strings/basic.jl
index 49ec6c369a84e..75cc61d2923e5 100644
--- a/test/strings/basic.jl
+++ b/test/strings/basic.jl
@@ -258,7 +258,7 @@ let s = normalize_string("tést",:NFKC)
 end
 @test_throws ArgumentError Base.unsafe_convert(Cstring, Base.cconvert(Cstring, "ba\0d"))
 
-cstrdup(s) = @static is_windows() ? ccall(:_strdup, Cstring, (Cstring,), s) : ccall(:strdup, Cstring, (Cstring,), s)
+cstrdup(s) = @static Sys.iswindows() ? ccall(:_strdup, Cstring, (Cstring,), s) : ccall(:strdup, Cstring, (Cstring,), s)
 let p = cstrdup("hello")
     @test unsafe_string(p) == "hello"
     Libc.free(p)