diff --git a/base/methodshow.jl b/base/methodshow.jl
index d1f9a0fdf0846..18a1ecbf09f11 100644
--- a/base/methodshow.jl
+++ b/base/methodshow.jl
@@ -174,6 +174,7 @@ 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, '\\', '/'))
     if inbase(M)
         if isempty(Base.GIT_VERSION_INFO.commit)
             # this url will only work if we're on a tagged release
@@ -190,7 +191,7 @@ function url(m::Method)
                     u = match(LibGit2.GITHUB_REGEX,u).captures[1]
                     commit = string(LibGit2.head_oid(repo))
                     root = LibGit2.path(repo)
-                    if startswith(file, root)
+                    if startswith(file, root) || startswith(realpath(file), root)
                         "https://github.com/$u/tree/$commit/"*file[length(root)+1:end]*"#L$line"
                     else
                         fileurl(file)
diff --git a/test/pkg.jl b/test/pkg.jl
index f815acb5816ef..65331f5bc259e 100644
--- a/test/pkg.jl
+++ b/test/pkg.jl
@@ -185,6 +185,13 @@ temp_pkg_dir() do
         Pkg.pin("Example", v"0.4.0")
         @test Pkg.update() == nothing
         Pkg.installed()["Example"] == v"0.4.0"
+
+        # bug identified in #16850, Base.url \ vs / for non-Base methods
+        include(Pkg.dir("Example","src","Example.jl"))
+        meth = first(methods(Example.domath))
+        fname = string(meth.file)
+        @test ('\\' in fname) == is_windows()
+        @test startswith(Base.url(meth), "https://github.com/JuliaLang/Example.jl/tree")
     end
 
     # add a directory that is not a git repository
diff --git a/test/reflection.jl b/test/reflection.jl
index 0a6a505e54555..7860e121de176 100644
--- a/test/reflection.jl
+++ b/test/reflection.jl
@@ -451,3 +451,50 @@ fLargeTable() = 4
 # issue #15280
 function f15280(x) end
 @test functionloc(f15280)[2] > 0
+
+# bug found in #16850, Base.url with backslashes on Windows
+function module_depth(from::Module, to::Module)
+    if from === to
+        return 0
+    else
+        return 1 + module_depth(from, module_parent(to))
+    end
+end
+function has_backslashes(mod::Module)
+    for n in names(mod, true, true)
+        isdefined(mod, n) || continue
+        f = getfield(mod, n)
+        if isa(f, Module) && module_depth(Main, f) <= module_depth(Main, mod)
+            continue
+        end
+        h = has_backslashes(f)
+        isnull(h) || return h
+    end
+    return Nullable{Method}()
+end
+function has_backslashes(f::Function)
+    for m in methods(f)
+        h = has_backslashes(m)
+        isnull(h) || return h
+    end
+    return Nullable{Method}()
+end
+function has_backslashes(meth::Method)
+    if '\\' in string(meth.file)
+        return Nullable{Method}(meth)
+    else
+        return Nullable{Method}()
+    end
+end
+has_backslashes(x) = Nullable{Method}()
+h16850 = has_backslashes(Base)
+if is_windows()
+    if isnull(h16850)
+        warn("No methods found in Base with backslashes in file name, ",
+             "skipping test for Base.url")
+    else
+        @test !('\\' in Base.url(get(h16850)))
+    end
+else
+    @test isnull(h16850)
+end