diff --git a/src/RestSharp/Options/RestClientOptions.cs b/src/RestSharp/Options/RestClientOptions.cs
index a07daf55d..49c197ffc 100644
--- a/src/RestSharp/Options/RestClientOptions.cs
+++ b/src/RestSharp/Options/RestClientOptions.cs
@@ -17,11 +17,16 @@
 using System.Net.Http.Headers;
 using System.Net.Security;
 using System.Reflection;
+using System.Runtime.Versioning;
 using System.Security.Cryptography.X509Certificates;
 using System.Text;
 using RestSharp.Authenticators;
 using RestSharp.Extensions;
 
+// ReSharper disable UnusedAutoPropertyAccessor.Global
+// ReSharper disable PropertyCanBeMadeInitOnly.Global
+// ReSharper disable AutoPropertyCanBeMadeGetOnly.Global
+
 namespace RestSharp;
 
 [GenerateImmutable]
@@ -62,6 +67,9 @@ public RestClientOptions(string baseUrl) : this(new Uri(Ensure.NotEmptyString(ba
     /// <summary>
     /// Passed to <see cref="HttpMessageHandler"/> <code>Credentials</code> property
     /// </summary>
+#if NET
+    [UnsupportedOSPlatform("browser")]
+#endif
     public ICredentials? Credentials { get; set; }
 
     /// <summary>
@@ -69,6 +77,9 @@ public RestClientOptions(string baseUrl) : this(new Uri(Ensure.NotEmptyString(ba
     /// running) will be sent along to the server. The default is false.
     /// Passed to <see cref="HttpMessageHandler"/> <code>UseDefaultCredentials</code> property
     /// </summary>
+#if NET
+    [UnsupportedOSPlatform("browser")]
+#endif
     public bool UseDefaultCredentials { get; set; }
 
     /// <summary>
@@ -80,6 +91,7 @@ public RestClientOptions(string baseUrl) : this(new Uri(Ensure.NotEmptyString(ba
     /// Set the decompression method to use when making requests
     /// </summary>
 #if NET
+    [UnsupportedOSPlatform("browser")]
     public DecompressionMethods AutomaticDecompression { get; set; } = DecompressionMethods.All;
 #else
     public DecompressionMethods AutomaticDecompression { get; set; } = DecompressionMethods.GZip;
@@ -88,16 +100,27 @@ public RestClientOptions(string baseUrl) : this(new Uri(Ensure.NotEmptyString(ba
     /// <summary>
     /// Set the maximum number of redirects to follow
     /// </summary>
+#if NET
+    [UnsupportedOSPlatform("browser")]
+#endif
     public int? MaxRedirects { get; set; }
 
     /// <summary>
     /// X509CertificateCollection to be sent with request
     /// </summary>
+#if NET
+    [UnsupportedOSPlatform("browser")]
+#endif
     public X509CertificateCollection? ClientCertificates { get; set; }
 
     /// <summary>
     /// Set the proxy to use when making requests. Default is null, which will use the default system proxy if one is set.
     /// </summary>
+#if NET
+    [UnsupportedOSPlatform("browser")]
+    [UnsupportedOSPlatform("ios")]
+    [UnsupportedOSPlatform("tvos")]
+#endif
     public IWebProxy? Proxy { get; set; }
 
     /// <summary>
@@ -123,12 +146,18 @@ public RestClientOptions(string baseUrl) : this(new Uri(Ensure.NotEmptyString(ba
     /// <summary>
     /// Passed to <see cref="HttpMessageHandler"/> <see langword="PreAuthenticate"/> property
     /// </summary>
+#if NET
+    [UnsupportedOSPlatform("browser")]
+#endif
     public bool PreAuthenticate { get; set; }
 
     /// <summary>
     /// Callback function for handling the validation of remote certificates. Useful for certificate pinning and
     /// overriding certificate errors in the scope of a request.
     /// </summary>
+#if NET
+    [UnsupportedOSPlatform("browser")]
+#endif
     public RemoteCertificateValidationCallback? RemoteCertificateValidationCallback { get; set; }
 
     /// <summary>
diff --git a/src/RestSharp/RestClient.cs b/src/RestSharp/RestClient.cs
index ec1c3f375..d4ae91867 100644
--- a/src/RestSharp/RestClient.cs
+++ b/src/RestSharp/RestClient.cs
@@ -226,26 +226,38 @@ static void ConfigureHttpClient(HttpClient httpClient, RestClientOptions options
         if (options.Expect100Continue != null) httpClient.DefaultRequestHeaders.ExpectContinue = options.Expect100Continue;
     }
 
+    // ReSharper disable once CognitiveComplexity
     static void ConfigureHttpMessageHandler(HttpClientHandler handler, ReadOnlyRestClientOptions options) {
-        handler.UseCookies             = false;
-        handler.Credentials            = options.Credentials;
-        handler.UseDefaultCredentials  = options.UseDefaultCredentials;
-        handler.AutomaticDecompression = options.AutomaticDecompression;
-        handler.PreAuthenticate        = options.PreAuthenticate;
-        handler.AllowAutoRedirect      = options.FollowRedirects;
-
-        if (handler.SupportsProxy) handler.Proxy = options.Proxy;
-
-        if (options.RemoteCertificateValidationCallback != null)
-            handler.ServerCertificateCustomValidationCallback =
-                (request, cert, chain, errors) => options.RemoteCertificateValidationCallback(request, cert, chain, errors);
-
-        if (options.ClientCertificates != null) {
-            handler.ClientCertificates.AddRange(options.ClientCertificates);
-            handler.ClientCertificateOptions = ClientCertificateOption.Manual;
+#if NET
+        if (!OperatingSystem.IsBrowser()) {
+#endif
+            handler.UseCookies             = false;
+            handler.Credentials            = options.Credentials;
+            handler.UseDefaultCredentials  = options.UseDefaultCredentials;
+            handler.AutomaticDecompression = options.AutomaticDecompression;
+            handler.PreAuthenticate        = options.PreAuthenticate;
+            if (options.MaxRedirects.HasValue) handler.MaxAutomaticRedirections = options.MaxRedirects.Value;
+
+            if (options.RemoteCertificateValidationCallback != null)
+                handler.ServerCertificateCustomValidationCallback =
+                    (request, cert, chain, errors) => options.RemoteCertificateValidationCallback(request, cert, chain, errors);
+
+            if (options.ClientCertificates != null) {
+                handler.ClientCertificates.AddRange(options.ClientCertificates);
+                handler.ClientCertificateOptions = ClientCertificateOption.Manual;
+            }
+#if NET
         }
-
-        if (options.MaxRedirects.HasValue) handler.MaxAutomaticRedirections = options.MaxRedirects.Value;
+#endif
+        handler.AllowAutoRedirect = options.FollowRedirects;
+
+#if NET
+        if (!OperatingSystem.IsBrowser() && !OperatingSystem.IsIOS() && !OperatingSystem.IsTvOS()) {
+#endif
+            if (handler.SupportsProxy) handler.Proxy = options.Proxy;
+#if NET
+        }
+#endif
     }
 
     [MemberNotNull(nameof(Serializers))]