diff --git a/src/Flurl.Http.CodeGen/ExtensionMethodModel.cs b/src/Flurl.Http.CodeGen/ExtensionMethodModel.cs
index 6fa88eb6..7a822602 100644
--- a/src/Flurl.Http.CodeGen/ExtensionMethodModel.cs
+++ b/src/Flurl.Http.CodeGen/ExtensionMethodModel.cs
@@ -9,7 +9,7 @@ public static IEnumerable<ExtensionMethodModel> GetAll() {
 			return
 				from httpVerb in new[] { null, "Get", "Post", "Head", "Put", "Delete", "Patch" }
 				from bodyType in new[] { null, "Json", /*"Xml",*/ "String", "UrlEncoded" }
-				from extensionType in new[] { "FlurlClient", "Url", "string" }
+				from extensionType in new[] { "IFlurlClient", "Url", "string" }
 				where SupportedCombo(httpVerb, bodyType, extensionType)
 				from deserializeType in new[] { null, "Json", "JsonList", /*"Xml",*/ "String", "Stream", "Bytes" }
 				where httpVerb == "Get" || deserializeType == null
@@ -27,7 +27,7 @@ where AllowDeserializeToGeneric(deserializeType) || !isGeneric
 		private static bool SupportedCombo(string verb, string bodyType, string extensionType) {
 			switch (verb) {
 				case null: // Send
-					return bodyType != null || extensionType != "FlurlClient";
+					return bodyType != null || extensionType != "IFlurlClient";
 				case "Post":
 					return true;
 				case "Put":
diff --git a/src/Flurl.Http.CodeGen/Program.cs b/src/Flurl.Http.CodeGen/Program.cs
index 2c910e88..62234b13 100644
--- a/src/Flurl.Http.CodeGen/Program.cs
+++ b/src/Flurl.Http.CodeGen/Program.cs
@@ -66,14 +66,14 @@ private static void WriteExtensionMethods(CodeWriter writer)
 		            name = xm.Name;
 	            }
 	            writer.WriteLine("/// <summary>");
-                var summaryStart = (xm.ExtentionOfType == "FlurlClient") ? "Sends" : "Creates a FlurlClient from the URL and sends";
+                var summaryStart = (xm.ExtentionOfType == "IFlurlClient") ? "Sends" : "Creates a FlurlClient from the URL and sends";
 				if (xm.HttpVerb == null)
 					writer.WriteLine("/// @0 an asynchronous request.", summaryStart);
 				else
 					writer.WriteLine("/// @0 an asynchronous @1 request.", summaryStart, xm.HttpVerb.ToUpperInvariant());
                 writer.WriteLine("/// </summary>");
-				if (xm.ExtentionOfType == "FlurlClient")
-                    writer.WriteLine("/// <param name=\"client\">The Flurl client.</param>");
+				if (xm.ExtentionOfType == "IFlurlClient")
+                    writer.WriteLine("/// <param name=\"client\">The IFlurlClient instance.</param>");
                 if (xm.ExtentionOfType == "Url" || xm.ExtentionOfType == "string")
                     writer.WriteLine("/// <param name=\"url\">The URL.</param>");
 				if (xm.HttpVerb == null)
@@ -87,7 +87,7 @@ private static void WriteExtensionMethods(CodeWriter writer)
 				writer.WriteLine("/// <returns>A Task whose result is @0.</returns>", xm.ReturnTypeDescription);
 
                 var args = new List<string>();
-                args.Add("this " + xm.ExtentionOfType + (xm.ExtentionOfType == "FlurlClient" ? " client" : " url"));
+                args.Add("this " + xm.ExtentionOfType + (xm.ExtentionOfType == "IFlurlClient" ? " client" : " url"));
 	            if (xm.HttpVerb == null)
 		            args.Add("HttpMethod verb");
                 if (xm.BodyType != null)
@@ -101,7 +101,7 @@ private static void WriteExtensionMethods(CodeWriter writer)
 
 				writer.WriteLine("public static Task<@0> @1@2(@3) {", xm.TaskArg, xm.Name, xm.IsGeneric ? "<T>" : "", string.Join(", ", args));
 
-                if (xm.ExtentionOfType == "FlurlClient")
+                if (xm.ExtentionOfType == "IFlurlClient")
                 {
 	                args.Clear();
                     args.Add(
@@ -121,7 +121,7 @@ private static void WriteExtensionMethods(CodeWriter writer)
 			                xm.BodyType == "String" ? "data" : $"client.Settings.{xm.BodyType}Serializer.Serialize(data)");
 	                }
 
-                    var client = (xm.ExtentionOfType == "FlurlClient") ? "client" : "new FlurlClient(url, false)";
+                    var client = (xm.ExtentionOfType == "IFlurlClient") ? "client" : "new FlurlClient(url, false)";
                     var receive = (xm.DeserializeToType == null) ? "" : string.Format(".Receive{0}{1}()", xm.DeserializeToType, xm.IsGeneric ? "<T>" : "");
                     writer.WriteLine("return @0.SendAsync(@1)@2;", client, string.Join(", ", args), receive);
                 }
diff --git a/src/Flurl.Http.Shared/ClientConfigExtensions.cs b/src/Flurl.Http.Shared/ClientConfigExtensions.cs
index 067707d7..ede3fdd1 100644
--- a/src/Flurl.Http.Shared/ClientConfigExtensions.cs
+++ b/src/Flurl.Http.Shared/ClientConfigExtensions.cs
@@ -15,13 +15,13 @@ namespace Flurl.Http
 	public static class ClientConfigExtensions
 	{
 		/// <summary>
-		/// Returns a new FlurlClient where all state (HttpClient, etc) is shared but with a different URL.
+		/// Returns a new IFlurlClient where all state (HttpClient, etc) is shared but with a different URL.
 		/// Allows you to re-use the underlying HttpClient instance (such as to share cookies, etc) with
 		/// different URLs in a thread-safe way.
 		/// </summary>
 		/// <param name="client">The client.</param>
 		/// <param name="url">The Url to call.</param>
-		public static FlurlClient WithUrl(this FlurlClient client, Url url) {
+		public static IFlurlClient WithUrl(this IFlurlClient client, Url url) {
 			var fc = client.Clone();
 			fc.Url = url;
 			// prevent the new client from automatically disposing the parent's HttpClient
@@ -30,22 +30,22 @@ public static FlurlClient WithUrl(this FlurlClient client, Url url) {
 		}
 
 		/// <summary>
-		/// Fluently specify that an existing FlurlClient should be used to call the Url, rather than creating a new one.
+		/// Fluently specify that an existing IFlurlClient should be used to call the Url, rather than creating a new one.
 		/// Enables re-using the underlying HttpClient.
 		/// </summary>
 		/// <param name="url">The URL.</param>
-		/// <param name="client">The FlurlClient to use in calling the Url</param>
-		public static FlurlClient WithClient(this Url url, FlurlClient client) {
+		/// <param name="client">The IFlurlClient to use in calling the Url</param>
+		public static IFlurlClient WithClient(this Url url, IFlurlClient client) {
 			return client.WithUrl(url);
 		}
 
 		/// <summary>
-		/// Fluently specify that an existing FlurlClient should be used to call the Url, rather than creating a new one.
+		/// Fluently specify that an existing IFlurlClient should be used to call the Url, rather than creating a new one.
 		/// Enables re-using the underlying HttpClient.
 		/// </summary>
 		/// <param name="url">The URL.</param>
-		/// <param name="client">The FlurlClient to use in calling the Url</param>
-		public static FlurlClient WithClient(this string url, FlurlClient client) {
+		/// <param name="client">The IFlurlClient to use in calling the Url</param>
+		public static IFlurlClient WithClient(this string url, IFlurlClient client) {
 			return client.WithUrl(url);
 		}
 
@@ -54,8 +54,8 @@ public static FlurlClient WithClient(this string url, FlurlClient client) {
 		/// </summary>
 		/// <param name="client">The client.</param>
 		/// <param name="action">Action defining the settings changes.</param>
-		/// <returns>The FlurlClient with the modified HttpClient</returns>
-		public static FlurlClient ConfigureClient(this FlurlClient client, Action<FlurlHttpSettings> action) {
+		/// <returns>The IFlurlClient with the modified HttpClient</returns>
+		public static IFlurlClient ConfigureClient(this IFlurlClient client, Action<FlurlHttpSettings> action) {
 			action(client.Settings);
 			return client;
 		}
@@ -65,8 +65,8 @@ public static FlurlClient ConfigureClient(this FlurlClient client, Action<FlurlH
 		/// </summary>
 		/// <param name="url">The URL.</param>
 		/// <param name="action">Action defining the settings changes.</param>
-		/// <returns>The FlurlClient with the modified HttpClient</returns>
-		public static FlurlClient ConfigureClient(this Url url, Action<FlurlHttpSettings> action) {
+		/// <returns>The IFlurlClient with the modified HttpClient</returns>
+		public static IFlurlClient ConfigureClient(this Url url, Action<FlurlHttpSettings> action) {
 			return new FlurlClient(url, true).ConfigureClient(action);
 		}
 
@@ -76,7 +76,7 @@ public static FlurlClient ConfigureClient(this Url url, Action<FlurlHttpSettings
 		/// <param name="url">The URL.</param>
 		/// <param name="action">Action defining the settings changes.</param>
 		/// <returns>The FlurlClient with the modified HttpClient</returns>
-		public static FlurlClient ConfigureClient(this string url, Action<FlurlHttpSettings> action) {
+		public static IFlurlClient ConfigureClient(this string url, Action<FlurlHttpSettings> action) {
 			return new FlurlClient(url, true).ConfigureClient(action);
 		}
 
@@ -86,7 +86,7 @@ public static FlurlClient ConfigureClient(this string url, Action<FlurlHttpSetti
 		/// <param name="client">The client.</param>
 		/// <param name="action">Action to perform on the HttpClient.</param>
 		/// <returns>The FlurlClient with the modified HttpClient</returns>
-		public static FlurlClient ConfigureHttpClient(this FlurlClient client, Action<HttpClient> action) {
+		public static IFlurlClient ConfigureHttpClient(this IFlurlClient client, Action<HttpClient> action) {
 			action(client.HttpClient);
 			return client;
 		}
@@ -97,7 +97,7 @@ public static FlurlClient ConfigureHttpClient(this FlurlClient client, Action<Ht
 		/// <param name="url">The URL.</param>
 		/// <param name="action">Action to perform on the HttpClient.</param>
 		/// <returns>The FlurlClient with the modified HttpClient</returns>
-		public static FlurlClient ConfigureHttpClient(this Url url, Action<HttpClient> action) {
+		public static IFlurlClient ConfigureHttpClient(this Url url, Action<HttpClient> action) {
 			return new FlurlClient(url, true).ConfigureHttpClient(action);
 		}
 
@@ -107,7 +107,7 @@ public static FlurlClient ConfigureHttpClient(this Url url, Action<HttpClient> a
 		/// <param name="url">The URL.</param>
 		/// <param name="action">Action to perform on the HttpClient.</param>
 		/// <returns>The FlurlClient with the modified HttpClient</returns>
-		public static FlurlClient ConfigureHttpClient(this string url, Action<HttpClient> action) {
+		public static IFlurlClient ConfigureHttpClient(this string url, Action<HttpClient> action) {
 			return new FlurlClient(url, true).ConfigureHttpClient(action);
 		}
 
@@ -117,7 +117,7 @@ public static FlurlClient ConfigureHttpClient(this string url, Action<HttpClient
 		/// <param name="client">The client.</param>
 		/// <param name="timespan">Time to wait before the request times out.</param>
 		/// <returns>The modified FlurlClient.</returns>
-		public static FlurlClient WithTimeout(this FlurlClient client, TimeSpan timespan) {
+		public static IFlurlClient WithTimeout(this IFlurlClient client, TimeSpan timespan) {
 			client.HttpClient.Timeout = timespan;
 			return client;
 		}
@@ -128,7 +128,7 @@ public static FlurlClient WithTimeout(this FlurlClient client, TimeSpan timespan
 		/// <param name="url">The URL.</param>
 		/// <param name="timespan">Time to wait before the request times out.</param>
 		/// <returns>The created FlurlClient.</returns>
-		public static FlurlClient WithTimeout(this Url url, TimeSpan timespan) {
+		public static IFlurlClient WithTimeout(this Url url, TimeSpan timespan) {
 			return new FlurlClient(url, true).WithTimeout(timespan);
 		}
 
@@ -138,7 +138,7 @@ public static FlurlClient WithTimeout(this Url url, TimeSpan timespan) {
 		/// <param name="url">The URL.</param>
 		/// <param name="timespan">Time to wait before the request times out.</param>
 		/// <returns>The created FlurlClient.</returns>
-		public static FlurlClient WithTimeout(this string url, TimeSpan timespan) {
+		public static IFlurlClient WithTimeout(this string url, TimeSpan timespan) {
 			return new FlurlClient(url, true).WithTimeout(timespan);
 		}
 
@@ -149,7 +149,7 @@ public static FlurlClient WithTimeout(this string url, TimeSpan timespan) {
 		/// <param name="seconds">Number of seconds to wait before the request times out.</param>
 		/// <returns>The modified FlurlClient.</returns>
 		/// <exception cref="OverflowException"><paramref name="seconds" /> is less than <see cref="F:System.TimeSpan.MinValue" /> or greater than <see cref="F:System.TimeSpan.MaxValue" />.-or-<paramref name="seconds" /> is <see cref="F:System.Double.PositiveInfinity" />.-or-<paramref name="seconds" /> is <see cref="F:System.Double.NegativeInfinity" />. </exception>
-		public static FlurlClient WithTimeout(this FlurlClient client, int seconds) {
+		public static IFlurlClient WithTimeout(this IFlurlClient client, int seconds) {
 			return client.WithTimeout(TimeSpan.FromSeconds(seconds));
 		}
 
@@ -160,7 +160,7 @@ public static FlurlClient WithTimeout(this FlurlClient client, int seconds) {
 		/// <param name="seconds">Number of seconds to wait before the request times out.</param>
 		/// <returns>The created FlurlClient.</returns>
 		/// <exception cref="OverflowException"><paramref name="seconds" /> is less than <see cref="F:System.TimeSpan.MinValue" /> or greater than <see cref="F:System.TimeSpan.MaxValue" />.-or-<paramref name="seconds" /> is <see cref="F:System.Double.PositiveInfinity" />.-or-<paramref name="seconds" /> is <see cref="F:System.Double.NegativeInfinity" />. </exception>
-		public static FlurlClient WithTimeout(this Url url, int seconds) {
+		public static IFlurlClient WithTimeout(this Url url, int seconds) {
 			return new FlurlClient(url, true).WithTimeout(seconds);
 		}
 
@@ -171,7 +171,7 @@ public static FlurlClient WithTimeout(this Url url, int seconds) {
 		/// <param name="seconds">Number of seconds to wait before the request times out.</param>
 		/// <returns>The created FlurlClient.</returns>
 		/// <exception cref="OverflowException"><paramref name="seconds" /> is less than <see cref="F:System.TimeSpan.MinValue" /> or greater than <see cref="F:System.TimeSpan.MaxValue" />.-or-<paramref name="seconds" /> is <see cref="F:System.Double.PositiveInfinity" />.-or-<paramref name="seconds" /> is <see cref="F:System.Double.NegativeInfinity" />. </exception>
-		public static FlurlClient WithTimeout(this string url, int seconds) {
+		public static IFlurlClient WithTimeout(this string url, int seconds) {
 			return new FlurlClient(url, true).WithTimeout(seconds);
 		}
 
@@ -182,7 +182,7 @@ public static FlurlClient WithTimeout(this string url, int seconds) {
 		/// <param name="name">HTTP header name.</param>
 		/// <param name="value">HTTP header value.</param>
 		/// <returns>The modified FlurlClient.</returns>
-		public static FlurlClient WithHeader(this FlurlClient client, string name, object value) {
+		public static IFlurlClient WithHeader(this IFlurlClient client, string name, object value) {
 			var values = new[] { value?.ToString() };
 			client.HttpClient.DefaultRequestHeaders.Add(name, values);
 			return client;
@@ -195,7 +195,7 @@ public static FlurlClient WithHeader(this FlurlClient client, string name, objec
 		/// <param name="name">HTTP header name.</param>
 		/// <param name="value">HTTP header value.</param>
 		/// <returns>The modified FlurlClient.</returns>
-		public static FlurlClient WithHeader(this Url url, string name, object value) {
+		public static IFlurlClient WithHeader(this Url url, string name, object value) {
 			return new FlurlClient(url, true).WithHeader(name, value);
 		}
 
@@ -206,7 +206,7 @@ public static FlurlClient WithHeader(this Url url, string name, object value) {
 		/// <param name="name">HTTP header name.</param>
 		/// <param name="value">HTTP header value.</param>
 		/// <returns>The modified FlurlClient.</returns>
-		public static FlurlClient WithHeader(this string url, string name, object value) {
+		public static IFlurlClient WithHeader(this string url, string name, object value) {
 			return new FlurlClient(url, true).WithHeader(name, value);
 		}
 
@@ -216,7 +216,7 @@ public static FlurlClient WithHeader(this string url, string name, object value)
 		/// <param name="client">The client.</param>
 		/// <param name="headers">Names/values of HTTP headers to set. Typically an anonymous object or IDictionary.</param>
 		/// <returns>The modified FlurlClient.</returns>
-		public static FlurlClient WithHeaders(this FlurlClient client, object headers) {
+		public static IFlurlClient WithHeaders(this IFlurlClient client, object headers) {
 			if (headers == null)
 				return client;
 
@@ -236,7 +236,7 @@ public static FlurlClient WithHeaders(this FlurlClient client, object headers) {
 		/// <param name="url">The URL.</param>
 		/// <param name="headers">Names/values of HTTP headers to set. Typically an anonymous object or IDictionary.</param>
 		/// <returns>The modified FlurlClient.</returns>
-		public static FlurlClient WithHeaders(this Url url, object headers) {
+		public static IFlurlClient WithHeaders(this Url url, object headers) {
 			return new FlurlClient(url, true).WithHeaders(headers);
 		}
 
@@ -246,7 +246,7 @@ public static FlurlClient WithHeaders(this Url url, object headers) {
 		/// <param name="url">The URL.</param>
 		/// <param name="headers">Names/values of HTTP headers to set. Typically an anonymous object or IDictionary.</param>
 		/// <returns>The modified FlurlClient.</returns>
-		public static FlurlClient WithHeaders(this string url, object headers) {
+		public static IFlurlClient WithHeaders(this string url, object headers) {
 			return new FlurlClient(url, true).WithHeaders(headers);
 		}
 
@@ -257,7 +257,7 @@ public static FlurlClient WithHeaders(this string url, object headers) {
 		/// <param name="username">Username of authenticating user.</param>
 		/// <param name="password">Password of authenticating user.</param>
 		/// <returns>The modified FlurlClient.</returns>
-		public static FlurlClient WithBasicAuth(this FlurlClient client, string username, string password) {
+		public static IFlurlClient WithBasicAuth(this IFlurlClient client, string username, string password) {
 			// http://stackoverflow.com/questions/14627399/setting-authorization-header-of-httpclient
 			var value = Convert.ToBase64String(Encoding.UTF8.GetBytes($"{username}:{password}"));
 			client.HttpClient.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Basic", value);
@@ -270,8 +270,8 @@ public static FlurlClient WithBasicAuth(this FlurlClient client, string username
 		/// <param name="url">The URL.</param>
 		/// <param name="username">Username of authenticating user.</param>
 		/// <param name="password">Password of authenticating user.</param>
-		/// <returns>The new FlurlClient.</returns>
-		public static FlurlClient WithBasicAuth(this Url url, string username, string password) {
+		/// <returns>The new IFlurlClient instance.</returns>
+		public static IFlurlClient WithBasicAuth(this Url url, string username, string password) {
 			return new FlurlClient(url, true).WithBasicAuth(username, password);
 		}
 
@@ -281,8 +281,8 @@ public static FlurlClient WithBasicAuth(this Url url, string username, string pa
 		/// <param name="url">The URL.</param>
 		/// <param name="username">Username of authenticating user.</param>
 		/// <param name="password">Password of authenticating user.</param>
-		/// <returns>The new FlurlClient.</returns>
-		public static FlurlClient WithBasicAuth(this string url, string username, string password) {
+		/// <returns>The new IFlurlClient instance.</returns>
+		public static IFlurlClient WithBasicAuth(this string url, string username, string password) {
 			return new FlurlClient(url, true).WithBasicAuth(username, password);
 		}
 
@@ -292,7 +292,7 @@ public static FlurlClient WithBasicAuth(this string url, string username, string
 		/// <param name="client">The client.</param>
 		/// <param name="token">The acquired bearer token to pass.</param>
 		/// <returns>The modified FlurlClient.</returns>
-		public static FlurlClient WithOAuthBearerToken(this FlurlClient client, string token) {
+		public static IFlurlClient WithOAuthBearerToken(this IFlurlClient client, string token) {
 			client.HttpClient.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", token);
 			return client;
 		}
@@ -302,8 +302,8 @@ public static FlurlClient WithOAuthBearerToken(this FlurlClient client, string t
 		/// </summary>
 		/// <param name="url">The URL.</param>
 		/// <param name="token">The acquired bearer token to pass.</param>
-		/// <returns>The new FlurlClient.</returns>
-		public static FlurlClient WithOAuthBearerToken(this Url url, string token) {
+		/// <returns>The new IFlurlClient instance.</returns>
+		public static IFlurlClient WithOAuthBearerToken(this Url url, string token) {
 			return new FlurlClient(url, true).WithOAuthBearerToken(token);
 		}
 
@@ -312,8 +312,8 @@ public static FlurlClient WithOAuthBearerToken(this Url url, string token) {
 		/// </summary>
 		/// <param name="url">The URL.</param>
 		/// <param name="token">The acquired bearer token to pass.</param>
-		/// <returns>The new FlurlClient.</returns>
-		public static FlurlClient WithOAuthBearerToken(this string url, string token) {
+		/// <returns>The new IFlurlClient instance.</returns>
+		public static IFlurlClient WithOAuthBearerToken(this string url, string token) {
 			return new FlurlClient(url, true).WithOAuthBearerToken(token);
 		}
 
@@ -323,7 +323,7 @@ public static FlurlClient WithOAuthBearerToken(this string url, string token) {
 		/// <param name="client">The client.</param>
 		/// <param name="pattern">Examples: "3xx", "100,300,600", "100-299,6xx"</param>
 		/// <returns>The modified FlurlClient.</returns>
-		public static FlurlClient AllowHttpStatus(this FlurlClient client, string pattern) {
+		public static IFlurlClient AllowHttpStatus(this IFlurlClient client, string pattern) {
 			if (!string.IsNullOrWhiteSpace(pattern)) {
 				var current = client.Settings.AllowedHttpStatusRange;
 				if (string.IsNullOrWhiteSpace(current))
@@ -339,8 +339,8 @@ public static FlurlClient AllowHttpStatus(this FlurlClient client, string patter
 		/// </summary>
 		/// <param name="url">The URL.</param>
 		/// <param name="pattern">Examples: "3xx", "100,300,600", "100-299,6xx"</param>
-		/// <returns>The new FlurlClient.</returns>
-		public static FlurlClient AllowHttpStatus(this Url url, string pattern) {
+		/// <returns>The new IFlurlClient instance.</returns>
+		public static IFlurlClient AllowHttpStatus(this Url url, string pattern) {
 			return new FlurlClient(url, true).AllowHttpStatus(pattern);
 		}
 
@@ -349,8 +349,8 @@ public static FlurlClient AllowHttpStatus(this Url url, string pattern) {
 		/// </summary>
 		/// <param name="url">The URL.</param>
 		/// <param name="pattern">Examples: "3xx", "100,300,600", "100-299,6xx"</param>
-		/// <returns>The new FlurlClient.</returns>
-		public static FlurlClient AllowHttpStatus(this string url, string pattern) {
+		/// <returns>The new IFlurlClient instance.</returns>
+		public static IFlurlClient AllowHttpStatus(this string url, string pattern) {
 			return new FlurlClient(url, true).AllowHttpStatus(pattern);
 		}
 
@@ -360,7 +360,7 @@ public static FlurlClient AllowHttpStatus(this string url, string pattern) {
 		/// <param name="client">The client.</param>
 		/// <param name="statusCodes">Examples: HttpStatusCode.NotFound</param>
 		/// <returns>The modified FlurlClient.</returns>
-		public static FlurlClient AllowHttpStatus(this FlurlClient client, params HttpStatusCode[] statusCodes) {
+		public static IFlurlClient AllowHttpStatus(this IFlurlClient client, params HttpStatusCode[] statusCodes) {
 			var pattern = string.Join(",", statusCodes.Select(c => (int)c));
 			return AllowHttpStatus(client, pattern);
 		}
@@ -370,8 +370,8 @@ public static FlurlClient AllowHttpStatus(this FlurlClient client, params HttpSt
 		/// </summary>
 		/// <param name="url">The URL.</param>
 		/// <param name="statusCodes">Examples: HttpStatusCode.NotFound</param>
-		/// <returns>The new FlurlClient.</returns>
-		public static FlurlClient AllowHttpStatus(this Url url, params HttpStatusCode[] statusCodes) {
+		/// <returns>The new IFlurlClient instance.</returns>
+		public static IFlurlClient AllowHttpStatus(this Url url, params HttpStatusCode[] statusCodes) {
 			return new FlurlClient(url, true).AllowHttpStatus(statusCodes);
 		}
 
@@ -380,16 +380,16 @@ public static FlurlClient AllowHttpStatus(this Url url, params HttpStatusCode[]
 		/// </summary>
 		/// <param name="url">The URL.</param>
 		/// <param name="statusCodes">Examples: HttpStatusCode.NotFound</param>
-		/// <returns>The new FlurlClient.</returns>
-		public static FlurlClient AllowHttpStatus(this string url, params HttpStatusCode[] statusCodes) {
+		/// <returns>The new IFlurlClient instance.</returns>
+		public static IFlurlClient AllowHttpStatus(this string url, params HttpStatusCode[] statusCodes) {
 			return new FlurlClient(url, true).AllowHttpStatus(statusCodes);
 		}
 
 		/// <summary>
 		/// Prevents a FlurlHttpException from being thrown on any completed response, regardless of the HTTP status code.
 		/// </summary>
-		/// <returns>The modified FlurlClient.</returns>
-		public static FlurlClient AllowAnyHttpStatus(this FlurlClient client) {
+		/// <returns>The modified IFlurlClient.</returns>
+		public static IFlurlClient AllowAnyHttpStatus(this IFlurlClient client) {
 			client.Settings.AllowedHttpStatusRange = "*";
 			return client;
 		}
@@ -397,16 +397,16 @@ public static FlurlClient AllowAnyHttpStatus(this FlurlClient client) {
 		/// <summary>
 		/// Creates a FlurlClient from the URL and prevents a FlurlHttpException from being thrown on any completed response, regardless of the HTTP status code.
 		/// </summary>
-		/// <returns>The new FlurlClient.</returns>
-		public static FlurlClient AllowAnyHttpStatus(this Url url) {
+		/// <returns>The new IFlurlClient instance.</returns>
+		public static IFlurlClient AllowAnyHttpStatus(this Url url) {
 			return new FlurlClient(url, true).AllowAnyHttpStatus();
 		}
 
 		/// <summary>
 		/// Creates a FlurlClient from the URL and prevents a FlurlHttpException from being thrown on any completed response, regardless of the HTTP status code.
 		/// </summary>
-		/// <returns>The new FlurlClient.</returns>
-		public static FlurlClient AllowAnyHttpStatus(this string url) {
+		/// <returns>The new IFlurlClient instance.</returns>
+		public static IFlurlClient AllowAnyHttpStatus(this string url) {
 			return new FlurlClient(url, true).AllowAnyHttpStatus();
 		}
 	}
diff --git a/src/Flurl.Http.Shared/CookieExtensions.cs b/src/Flurl.Http.Shared/CookieExtensions.cs
index 6fe312ba..52903884 100644
--- a/src/Flurl.Http.Shared/CookieExtensions.cs
+++ b/src/Flurl.Http.Shared/CookieExtensions.cs
@@ -18,7 +18,7 @@ public static class CookieExtensions
 		/// <summary>
 		/// Allows cookies to be sent and received in calls made with this client. Not necessary to call when setting cookies via WithCookie/WithCookies.
 		/// </summary>
-		public static FlurlClient EnableCookies(this FlurlClient client) {
+		public static IFlurlClient EnableCookies(this IFlurlClient client) {
 			client.Settings.CookiesEnabled = true;
 			return client;
 		}
@@ -26,14 +26,14 @@ public static FlurlClient EnableCookies(this FlurlClient client) {
 		/// <summary>
 		/// Allows cookies to be sent and received in calls made to this Url. Not necessary to call when setting cookies via WithCookie/WithCookies.
 		/// </summary>
-		public static FlurlClient EnableCookies(this Url url) {
+		public static IFlurlClient EnableCookies(this Url url) {
 			return new FlurlClient(url).EnableCookies();
 		}
 
 		/// <summary>
 		/// Allows cookies to be sent and received in calls made to this Url. Not necessary to call when setting cookies via WithCookie/WithCookies.
 		/// </summary>
-		public static FlurlClient EnableCookies(this string url) {
+		public static IFlurlClient EnableCookies(this string url) {
 			return new FlurlClient(url).EnableCookies();
 		}
 
@@ -44,7 +44,7 @@ public static FlurlClient EnableCookies(this string url) {
 		/// <param name="cookie">The cookie to set.</param>
 		/// <returns>The modified FlurlClient.</returns>
 		/// <exception cref="ArgumentNullException"><paramref name="cookie" /> is null.</exception>
-		public static FlurlClient WithCookie(this FlurlClient client, Cookie cookie) {
+		public static IFlurlClient WithCookie(this IFlurlClient client, Cookie cookie) {
 			client.Settings.CookiesEnabled = true;
 			client.Cookies[cookie.Name] = cookie;
 			return client;
@@ -57,7 +57,7 @@ public static FlurlClient WithCookie(this FlurlClient client, Cookie cookie) {
 		/// <param name="cookie">the cookie to set.</param>
 		/// <returns>The modified FlurlClient.</returns>
 		/// <exception cref="ArgumentNullException"><paramref name="cookie" /> is null.</exception>
-		public static FlurlClient WithCookie(this string url, Cookie cookie) {
+		public static IFlurlClient WithCookie(this string url, Cookie cookie) {
 			return new FlurlClient(url, true).WithCookie(cookie);
 		}
 
@@ -68,7 +68,7 @@ public static FlurlClient WithCookie(this string url, Cookie cookie) {
 		/// <param name="cookie">the cookie to set.</param>
 		/// <returns>The modified FlurlClient.</returns>
 		/// <exception cref="ArgumentNullException"><paramref name="cookie" /> is null.</exception>
-		public static FlurlClient WithCookie(this Url url, Cookie cookie) {
+		public static IFlurlClient WithCookie(this Url url, Cookie cookie) {
 			return new FlurlClient(url, true).WithCookie(cookie);
 		}
 
@@ -81,7 +81,7 @@ public static FlurlClient WithCookie(this Url url, Cookie cookie) {
 		/// <param name="expires">cookie expiration (optional). If excluded, cookie only lives for duration of session.</param>
 		/// <returns>The modified FlurlClient.</returns>
 		/// <exception cref="ArgumentNullException"><paramref name="value" /> is null.</exception>
-		public static FlurlClient WithCookie(this FlurlClient client, string name, object value, DateTime? expires = null) {
+		public static IFlurlClient WithCookie(this IFlurlClient client, string name, object value, DateTime? expires = null) {
 			var cookie = new Cookie(name, value?.ToInvariantString()) { Expires = expires ?? DateTime.MinValue };
 			return client.WithCookie(cookie);
 		}
@@ -95,7 +95,7 @@ public static FlurlClient WithCookie(this FlurlClient client, string name, objec
 	    /// <param name="expires">cookie expiration (optional). If excluded, cookie only lives for duration of session.</param>
 	    /// <returns>The modified FlurlClient.</returns>
 	    /// <exception cref="ArgumentNullException"><paramref name="value" /> is null.</exception>
-	    public static FlurlClient WithCookie(this string url, string name, object value, DateTime? expires = null) {
+	    public static IFlurlClient WithCookie(this string url, string name, object value, DateTime? expires = null) {
 			return new FlurlClient(url, true).WithCookie(name, value, expires);
 		}
 
@@ -108,7 +108,7 @@ public static FlurlClient WithCookie(this string url, string name, object value,
 	    /// <param name="expires">cookie expiration (optional). If excluded, cookie only lives for duration of session.</param>
 	    /// <returns>The modified FlurlClient.</returns>
 	    /// <exception cref="ArgumentNullException"><paramref name="value" /> is null.</exception>
-	    public static FlurlClient WithCookie(this Url url, string name, object value, DateTime? expires = null) {
+	    public static IFlurlClient WithCookie(this Url url, string name, object value, DateTime? expires = null) {
 			return new FlurlClient(url, true).WithCookie(name, value, expires);
 		}
 
@@ -120,7 +120,7 @@ public static FlurlClient WithCookie(this Url url, string name, object value, Da
 	    /// <param name="expires">Expiration for all cookies (optional). If excluded, cookies only live for duration of session.</param>
 	    /// <returns>The modified FlurlClient.</returns>
 	    /// <exception cref="ArgumentNullException"><paramref name="cookies" /> is null.</exception>
-	    public static FlurlClient WithCookies(this FlurlClient client, object cookies, DateTime? expires = null) {
+	    public static IFlurlClient WithCookies(this IFlurlClient client, object cookies, DateTime? expires = null) {
 			if (cookies == null)
 				return client;
 
@@ -138,7 +138,7 @@ public static FlurlClient WithCookies(this FlurlClient client, object cookies, D
 	    /// <param name="expires">Expiration for all cookies (optional). If excluded, cookies only live for duration of session.</param>
 	    /// <returns>The modified FlurlClient.</returns>
 	    /// <exception cref="ArgumentNullException"><paramref name="cookies" /> is null.</exception>
-	    public static FlurlClient WithCookies(this Url url, object cookies, DateTime? expires = null) {
+	    public static IFlurlClient WithCookies(this Url url, object cookies, DateTime? expires = null) {
 			return new FlurlClient(url, true).WithCookies(cookies);
 		}
 
@@ -150,7 +150,7 @@ public static FlurlClient WithCookies(this Url url, object cookies, DateTime? ex
 	    /// <param name="expires">Expiration for all cookies (optional). If excluded, cookies only live for duration of session.</param>
 	    /// <returns>The modified FlurlClient.</returns>
 	    /// <exception cref="ArgumentNullException"><paramref name="cookies" /> is null.</exception>
-	    public static FlurlClient WithCookies(this string url, object cookies, DateTime? expires = null) {
+	    public static IFlurlClient WithCookies(this string url, object cookies, DateTime? expires = null) {
 			return new FlurlClient(url, true).WithCookies(cookies);
 		}
 	}
diff --git a/src/Flurl.Http.Shared/DownloadExtensions.cs b/src/Flurl.Http.Shared/DownloadExtensions.cs
index 66beca09..6be61bb2 100644
--- a/src/Flurl.Http.Shared/DownloadExtensions.cs
+++ b/src/Flurl.Http.Shared/DownloadExtensions.cs
@@ -17,7 +17,7 @@ public static class DownloadExtensions
 		/// <param name="localFileName">Name of local file. If not specified, the source filename (last segment of the URL) is used.</param>
 		/// <param name="bufferSize">Buffer size in bytes. Default is 4096.</param>
 		/// <returns>A Task whose result is the local path of the downloaded file.</returns>
-		public static async Task<string> DownloadFileAsync(this FlurlClient client, string localFolderPath, string localFileName = null, int bufferSize = 4096) {
+		public static async Task<string> DownloadFileAsync(this IFlurlClient client, string localFolderPath, string localFileName = null, int bufferSize = 4096) {
 			if (localFileName == null)
 				localFileName = client.Url.Path.Split('/').Last();
 
diff --git a/src/Flurl.Http.Shared/FlurlClient.cs b/src/Flurl.Http.Shared/FlurlClient.cs
index 2cbd7cd4..5c01c49f 100644
--- a/src/Flurl.Http.Shared/FlurlClient.cs
+++ b/src/Flurl.Http.Shared/FlurlClient.cs
@@ -10,10 +10,58 @@
 
 namespace Flurl.Http
 {
+	/// <summary>
+	/// Interface defining FlurlClient's contract (useful for mocking and DI)
+	/// </summary>
+	public interface IFlurlClient : IDisposable {
+		/// <summary>
+		/// Creates a copy of this FlurlClient with a shared instance of HttpClient and HttpMessageHandler
+		/// </summary>
+		FlurlClient Clone();
+
+		/// <summary>
+		/// Gets or sets the FlurlHttpSettings object used by this client.
+		/// </summary>
+		FlurlHttpSettings Settings { get; set; }
+
+		/// <summary>
+		/// Gets or sets the URL to be called.
+		/// </summary>
+		Url Url { get; set; }
+
+		/// <summary>
+		/// Collection of HttpCookies sent and received.
+		/// </summary>
+		IDictionary<string, Cookie> Cookies { get; }
+
+		/// <summary>
+		/// Gets the HttpClient to be used in subsequent HTTP calls. Creation (when necessary) is delegated
+		/// to FlurlHttp.HttpClientFactory. Reused for the life of the FlurlClient.
+		/// </summary>
+		HttpClient HttpClient { get; }
+
+		/// <summary>
+		/// Gets the HttpMessageHandler to be used in subsequent HTTP calls. Creation (when necessary) is delegated
+		/// to FlurlHttp.HttpClientFactory.
+		/// </summary>
+		HttpMessageHandler HttpMessageHandler { get; }
+
+		/// <summary>
+		/// Creates and asynchronously sends an HttpRequestMethod, disposing HttpClient if AutoDispose it true.
+		/// Mainly used to implement higher-level extension methods (GetJsonAsync, etc).
+		/// </summary>
+		/// <param name="verb">The HTTP method used to make the request.</param>
+		/// <param name="content">Contents of the request body.</param>
+		/// <param name="cancellationToken">A cancellation token that can be used by other objects or threads to receive notice of cancellation. Optional.</param>
+		/// <param name="completionOption">The HttpCompletionOption used in the request. Optional.</param>
+		/// <returns>A Task whose result is the received HttpResponseMessage.</returns>
+		Task<HttpResponseMessage> SendAsync(HttpMethod verb, HttpContent content = null, CancellationToken? cancellationToken = null, HttpCompletionOption completionOption = HttpCompletionOption.ResponseContentRead);
+	}
+
 	/// <summary>
 	/// A chainable wrapper around HttpClient and Flurl.Url.
 	/// </summary>
-	public class FlurlClient : IDisposable
+	public class FlurlClient : IFlurlClient
 	{
 		/// <summary>
 		/// Initializes a new instance of the <see cref="FlurlClient"/> class.
diff --git a/src/Flurl.Http.Shared/HttpExtensions.cs b/src/Flurl.Http.Shared/HttpExtensions.cs
index 5bc6c347..9ddbc857 100644
--- a/src/Flurl.Http.Shared/HttpExtensions.cs
+++ b/src/Flurl.Http.Shared/HttpExtensions.cs
@@ -43,13 +43,13 @@ public static class HttpExtensions
 		/// <summary>
 		/// Sends an asynchronous request.
 		/// </summary>
-		/// <param name="client">The Flurl client.</param>
+		/// <param name="client">The IFlurlClient instance.</param>
 		/// <param name="verb">The HTTP method used to make the request.</param>
 		/// <param name="data">Contents of the request body.</param>
 		/// <param name="cancellationToken">A cancellation token that can be used by other objects or threads to receive notice of cancellation. Optional.</param>
 		/// <param name="completionOption">The HttpCompletionOption used in the request. Optional.</param>
 		/// <returns>A Task whose result is the received HttpResponseMessage.</returns>
-		public static Task<HttpResponseMessage> SendJsonAsync(this FlurlClient client, HttpMethod verb, object data, CancellationToken cancellationToken = default(CancellationToken), HttpCompletionOption completionOption = HttpCompletionOption.ResponseContentRead) {
+		public static Task<HttpResponseMessage> SendJsonAsync(this IFlurlClient client, HttpMethod verb, object data, CancellationToken cancellationToken = default(CancellationToken), HttpCompletionOption completionOption = HttpCompletionOption.ResponseContentRead) {
 			var content = new CapturedJsonContent(client.Settings.JsonSerializer.Serialize(data));
 			return client.SendAsync(verb, content: content, cancellationToken: cancellationToken, completionOption: completionOption);
 		}
@@ -83,13 +83,13 @@ public static class HttpExtensions
 		/// <summary>
 		/// Sends an asynchronous request.
 		/// </summary>
-		/// <param name="client">The Flurl client.</param>
+		/// <param name="client">The IFlurlClient instance.</param>
 		/// <param name="verb">The HTTP method used to make the request.</param>
 		/// <param name="data">Contents of the request body.</param>
 		/// <param name="cancellationToken">A cancellation token that can be used by other objects or threads to receive notice of cancellation. Optional.</param>
 		/// <param name="completionOption">The HttpCompletionOption used in the request. Optional.</param>
 		/// <returns>A Task whose result is the received HttpResponseMessage.</returns>
-		public static Task<HttpResponseMessage> SendStringAsync(this FlurlClient client, HttpMethod verb, string data, CancellationToken cancellationToken = default(CancellationToken), HttpCompletionOption completionOption = HttpCompletionOption.ResponseContentRead) {
+		public static Task<HttpResponseMessage> SendStringAsync(this IFlurlClient client, HttpMethod verb, string data, CancellationToken cancellationToken = default(CancellationToken), HttpCompletionOption completionOption = HttpCompletionOption.ResponseContentRead) {
 			var content = new CapturedStringContent(data);
 			return client.SendAsync(verb, content: content, cancellationToken: cancellationToken, completionOption: completionOption);
 		}
@@ -123,13 +123,13 @@ public static class HttpExtensions
 		/// <summary>
 		/// Sends an asynchronous request.
 		/// </summary>
-		/// <param name="client">The Flurl client.</param>
+		/// <param name="client">The IFlurlClient instance.</param>
 		/// <param name="verb">The HTTP method used to make the request.</param>
 		/// <param name="data">Contents of the request body.</param>
 		/// <param name="cancellationToken">A cancellation token that can be used by other objects or threads to receive notice of cancellation. Optional.</param>
 		/// <param name="completionOption">The HttpCompletionOption used in the request. Optional.</param>
 		/// <returns>A Task whose result is the received HttpResponseMessage.</returns>
-		public static Task<HttpResponseMessage> SendUrlEncodedAsync(this FlurlClient client, HttpMethod verb, object data, CancellationToken cancellationToken = default(CancellationToken), HttpCompletionOption completionOption = HttpCompletionOption.ResponseContentRead) {
+		public static Task<HttpResponseMessage> SendUrlEncodedAsync(this IFlurlClient client, HttpMethod verb, object data, CancellationToken cancellationToken = default(CancellationToken), HttpCompletionOption completionOption = HttpCompletionOption.ResponseContentRead) {
 			var content = new CapturedUrlEncodedContent(client.Settings.UrlEncodedSerializer.Serialize(data));
 			return client.SendAsync(verb, content: content, cancellationToken: cancellationToken, completionOption: completionOption);
 		}
@@ -163,77 +163,77 @@ public static class HttpExtensions
 		/// <summary>
 		/// Sends an asynchronous GET request.
 		/// </summary>
-		/// <param name="client">The Flurl client.</param>
+		/// <param name="client">The IFlurlClient instance.</param>
 		/// <param name="cancellationToken">A cancellation token that can be used by other objects or threads to receive notice of cancellation. Optional.</param>
 		/// <param name="completionOption">The HttpCompletionOption used in the request. Optional.</param>
 		/// <returns>A Task whose result is the received HttpResponseMessage.</returns>
-		public static Task<HttpResponseMessage> GetAsync(this FlurlClient client, CancellationToken cancellationToken = default(CancellationToken), HttpCompletionOption completionOption = HttpCompletionOption.ResponseContentRead) {
+		public static Task<HttpResponseMessage> GetAsync(this IFlurlClient client, CancellationToken cancellationToken = default(CancellationToken), HttpCompletionOption completionOption = HttpCompletionOption.ResponseContentRead) {
 			return client.SendAsync(HttpMethod.Get, cancellationToken: cancellationToken, completionOption: completionOption);
 		}
 
 		/// <summary>
 		/// Sends an asynchronous GET request.
 		/// </summary>
-		/// <param name="client">The Flurl client.</param>
+		/// <param name="client">The IFlurlClient instance.</param>
 		/// <param name="cancellationToken">A cancellation token that can be used by other objects or threads to receive notice of cancellation. Optional.</param>
 		/// <param name="completionOption">The HttpCompletionOption used in the request. Optional.</param>
 		/// <returns>A Task whose result is the JSON response body deserialized to an object of type T.</returns>
-		public static Task<T> GetJsonAsync<T>(this FlurlClient client, CancellationToken cancellationToken = default(CancellationToken), HttpCompletionOption completionOption = HttpCompletionOption.ResponseContentRead) {
+		public static Task<T> GetJsonAsync<T>(this IFlurlClient client, CancellationToken cancellationToken = default(CancellationToken), HttpCompletionOption completionOption = HttpCompletionOption.ResponseContentRead) {
 			return client.SendAsync(HttpMethod.Get, cancellationToken: cancellationToken, completionOption: completionOption).ReceiveJson<T>();
 		}
 
 		/// <summary>
 		/// Sends an asynchronous GET request.
 		/// </summary>
-		/// <param name="client">The Flurl client.</param>
+		/// <param name="client">The IFlurlClient instance.</param>
 		/// <param name="cancellationToken">A cancellation token that can be used by other objects or threads to receive notice of cancellation. Optional.</param>
 		/// <param name="completionOption">The HttpCompletionOption used in the request. Optional.</param>
 		/// <returns>A Task whose result is the JSON response body deserialized to a dynamic.</returns>
-		public static Task<dynamic> GetJsonAsync(this FlurlClient client, CancellationToken cancellationToken = default(CancellationToken), HttpCompletionOption completionOption = HttpCompletionOption.ResponseContentRead) {
+		public static Task<dynamic> GetJsonAsync(this IFlurlClient client, CancellationToken cancellationToken = default(CancellationToken), HttpCompletionOption completionOption = HttpCompletionOption.ResponseContentRead) {
 			return client.SendAsync(HttpMethod.Get, cancellationToken: cancellationToken, completionOption: completionOption).ReceiveJson();
 		}
 
 		/// <summary>
 		/// Sends an asynchronous GET request.
 		/// </summary>
-		/// <param name="client">The Flurl client.</param>
+		/// <param name="client">The IFlurlClient instance.</param>
 		/// <param name="cancellationToken">A cancellation token that can be used by other objects or threads to receive notice of cancellation. Optional.</param>
 		/// <param name="completionOption">The HttpCompletionOption used in the request. Optional.</param>
 		/// <returns>A Task whose result is the JSON response body deserialized to a list of dynamics.</returns>
-		public static Task<IList<dynamic>> GetJsonListAsync(this FlurlClient client, CancellationToken cancellationToken = default(CancellationToken), HttpCompletionOption completionOption = HttpCompletionOption.ResponseContentRead) {
+		public static Task<IList<dynamic>> GetJsonListAsync(this IFlurlClient client, CancellationToken cancellationToken = default(CancellationToken), HttpCompletionOption completionOption = HttpCompletionOption.ResponseContentRead) {
 			return client.SendAsync(HttpMethod.Get, cancellationToken: cancellationToken, completionOption: completionOption).ReceiveJsonList();
 		}
 
 		/// <summary>
 		/// Sends an asynchronous GET request.
 		/// </summary>
-		/// <param name="client">The Flurl client.</param>
+		/// <param name="client">The IFlurlClient instance.</param>
 		/// <param name="cancellationToken">A cancellation token that can be used by other objects or threads to receive notice of cancellation. Optional.</param>
 		/// <param name="completionOption">The HttpCompletionOption used in the request. Optional.</param>
 		/// <returns>A Task whose result is the response body as a string.</returns>
-		public static Task<string> GetStringAsync(this FlurlClient client, CancellationToken cancellationToken = default(CancellationToken), HttpCompletionOption completionOption = HttpCompletionOption.ResponseContentRead) {
+		public static Task<string> GetStringAsync(this IFlurlClient client, CancellationToken cancellationToken = default(CancellationToken), HttpCompletionOption completionOption = HttpCompletionOption.ResponseContentRead) {
 			return client.SendAsync(HttpMethod.Get, cancellationToken: cancellationToken, completionOption: completionOption).ReceiveString();
 		}
 
 		/// <summary>
 		/// Sends an asynchronous GET request.
 		/// </summary>
-		/// <param name="client">The Flurl client.</param>
+		/// <param name="client">The IFlurlClient instance.</param>
 		/// <param name="cancellationToken">A cancellation token that can be used by other objects or threads to receive notice of cancellation. Optional.</param>
 		/// <param name="completionOption">The HttpCompletionOption used in the request. Optional.</param>
 		/// <returns>A Task whose result is the response body as a Stream.</returns>
-		public static Task<Stream> GetStreamAsync(this FlurlClient client, CancellationToken cancellationToken = default(CancellationToken), HttpCompletionOption completionOption = HttpCompletionOption.ResponseContentRead) {
+		public static Task<Stream> GetStreamAsync(this IFlurlClient client, CancellationToken cancellationToken = default(CancellationToken), HttpCompletionOption completionOption = HttpCompletionOption.ResponseContentRead) {
 			return client.SendAsync(HttpMethod.Get, cancellationToken: cancellationToken, completionOption: completionOption).ReceiveStream();
 		}
 
 		/// <summary>
 		/// Sends an asynchronous GET request.
 		/// </summary>
-		/// <param name="client">The Flurl client.</param>
+		/// <param name="client">The IFlurlClient instance.</param>
 		/// <param name="cancellationToken">A cancellation token that can be used by other objects or threads to receive notice of cancellation. Optional.</param>
 		/// <param name="completionOption">The HttpCompletionOption used in the request. Optional.</param>
 		/// <returns>A Task whose result is the response body as a byte array.</returns>
-		public static Task<byte[]> GetBytesAsync(this FlurlClient client, CancellationToken cancellationToken = default(CancellationToken), HttpCompletionOption completionOption = HttpCompletionOption.ResponseContentRead) {
+		public static Task<byte[]> GetBytesAsync(this IFlurlClient client, CancellationToken cancellationToken = default(CancellationToken), HttpCompletionOption completionOption = HttpCompletionOption.ResponseContentRead) {
 			return client.SendAsync(HttpMethod.Get, cancellationToken: cancellationToken, completionOption: completionOption).ReceiveBytes();
 		}
 
@@ -394,12 +394,12 @@ public static class HttpExtensions
 		/// <summary>
 		/// Sends an asynchronous POST request.
 		/// </summary>
-		/// <param name="client">The Flurl client.</param>
+		/// <param name="client">The IFlurlClient instance.</param>
 		/// <param name="content">Contents of the request body.</param>
 		/// <param name="cancellationToken">A cancellation token that can be used by other objects or threads to receive notice of cancellation. Optional.</param>
 		/// <param name="completionOption">The HttpCompletionOption used in the request. Optional.</param>
 		/// <returns>A Task whose result is the received HttpResponseMessage.</returns>
-		public static Task<HttpResponseMessage> PostAsync(this FlurlClient client, HttpContent content, CancellationToken cancellationToken = default(CancellationToken), HttpCompletionOption completionOption = HttpCompletionOption.ResponseContentRead) {
+		public static Task<HttpResponseMessage> PostAsync(this IFlurlClient client, HttpContent content, CancellationToken cancellationToken = default(CancellationToken), HttpCompletionOption completionOption = HttpCompletionOption.ResponseContentRead) {
 			return client.SendAsync(HttpMethod.Post, content: content, cancellationToken: cancellationToken, completionOption: completionOption);
 		}
 
@@ -430,12 +430,12 @@ public static class HttpExtensions
 		/// <summary>
 		/// Sends an asynchronous POST request.
 		/// </summary>
-		/// <param name="client">The Flurl client.</param>
+		/// <param name="client">The IFlurlClient instance.</param>
 		/// <param name="data">Contents of the request body.</param>
 		/// <param name="cancellationToken">A cancellation token that can be used by other objects or threads to receive notice of cancellation. Optional.</param>
 		/// <param name="completionOption">The HttpCompletionOption used in the request. Optional.</param>
 		/// <returns>A Task whose result is the received HttpResponseMessage.</returns>
-		public static Task<HttpResponseMessage> PostJsonAsync(this FlurlClient client, object data, CancellationToken cancellationToken = default(CancellationToken), HttpCompletionOption completionOption = HttpCompletionOption.ResponseContentRead) {
+		public static Task<HttpResponseMessage> PostJsonAsync(this IFlurlClient client, object data, CancellationToken cancellationToken = default(CancellationToken), HttpCompletionOption completionOption = HttpCompletionOption.ResponseContentRead) {
 			var content = new CapturedJsonContent(client.Settings.JsonSerializer.Serialize(data));
 			return client.SendAsync(HttpMethod.Post, content: content, cancellationToken: cancellationToken, completionOption: completionOption);
 		}
@@ -467,12 +467,12 @@ public static class HttpExtensions
 		/// <summary>
 		/// Sends an asynchronous POST request.
 		/// </summary>
-		/// <param name="client">The Flurl client.</param>
+		/// <param name="client">The IFlurlClient instance.</param>
 		/// <param name="data">Contents of the request body.</param>
 		/// <param name="cancellationToken">A cancellation token that can be used by other objects or threads to receive notice of cancellation. Optional.</param>
 		/// <param name="completionOption">The HttpCompletionOption used in the request. Optional.</param>
 		/// <returns>A Task whose result is the received HttpResponseMessage.</returns>
-		public static Task<HttpResponseMessage> PostStringAsync(this FlurlClient client, string data, CancellationToken cancellationToken = default(CancellationToken), HttpCompletionOption completionOption = HttpCompletionOption.ResponseContentRead) {
+		public static Task<HttpResponseMessage> PostStringAsync(this IFlurlClient client, string data, CancellationToken cancellationToken = default(CancellationToken), HttpCompletionOption completionOption = HttpCompletionOption.ResponseContentRead) {
 			var content = new CapturedStringContent(data);
 			return client.SendAsync(HttpMethod.Post, content: content, cancellationToken: cancellationToken, completionOption: completionOption);
 		}
@@ -504,12 +504,12 @@ public static class HttpExtensions
 		/// <summary>
 		/// Sends an asynchronous POST request.
 		/// </summary>
-		/// <param name="client">The Flurl client.</param>
+		/// <param name="client">The IFlurlClient instance.</param>
 		/// <param name="data">Contents of the request body.</param>
 		/// <param name="cancellationToken">A cancellation token that can be used by other objects or threads to receive notice of cancellation. Optional.</param>
 		/// <param name="completionOption">The HttpCompletionOption used in the request. Optional.</param>
 		/// <returns>A Task whose result is the received HttpResponseMessage.</returns>
-		public static Task<HttpResponseMessage> PostUrlEncodedAsync(this FlurlClient client, object data, CancellationToken cancellationToken = default(CancellationToken), HttpCompletionOption completionOption = HttpCompletionOption.ResponseContentRead) {
+		public static Task<HttpResponseMessage> PostUrlEncodedAsync(this IFlurlClient client, object data, CancellationToken cancellationToken = default(CancellationToken), HttpCompletionOption completionOption = HttpCompletionOption.ResponseContentRead) {
 			var content = new CapturedUrlEncodedContent(client.Settings.UrlEncodedSerializer.Serialize(data));
 			return client.SendAsync(HttpMethod.Post, content: content, cancellationToken: cancellationToken, completionOption: completionOption);
 		}
@@ -541,11 +541,11 @@ public static class HttpExtensions
 		/// <summary>
 		/// Sends an asynchronous HEAD request.
 		/// </summary>
-		/// <param name="client">The Flurl client.</param>
+		/// <param name="client">The IFlurlClient instance.</param>
 		/// <param name="cancellationToken">A cancellation token that can be used by other objects or threads to receive notice of cancellation. Optional.</param>
 		/// <param name="completionOption">The HttpCompletionOption used in the request. Optional.</param>
 		/// <returns>A Task whose result is the received HttpResponseMessage.</returns>
-		public static Task<HttpResponseMessage> HeadAsync(this FlurlClient client, CancellationToken cancellationToken = default(CancellationToken), HttpCompletionOption completionOption = HttpCompletionOption.ResponseContentRead) {
+		public static Task<HttpResponseMessage> HeadAsync(this IFlurlClient client, CancellationToken cancellationToken = default(CancellationToken), HttpCompletionOption completionOption = HttpCompletionOption.ResponseContentRead) {
 			return client.SendAsync(HttpMethod.Head, cancellationToken: cancellationToken, completionOption: completionOption);
 		}
 
@@ -574,12 +574,12 @@ public static class HttpExtensions
 		/// <summary>
 		/// Sends an asynchronous PUT request.
 		/// </summary>
-		/// <param name="client">The Flurl client.</param>
+		/// <param name="client">The IFlurlClient instance.</param>
 		/// <param name="content">Contents of the request body.</param>
 		/// <param name="cancellationToken">A cancellation token that can be used by other objects or threads to receive notice of cancellation. Optional.</param>
 		/// <param name="completionOption">The HttpCompletionOption used in the request. Optional.</param>
 		/// <returns>A Task whose result is the received HttpResponseMessage.</returns>
-		public static Task<HttpResponseMessage> PutAsync(this FlurlClient client, HttpContent content, CancellationToken cancellationToken = default(CancellationToken), HttpCompletionOption completionOption = HttpCompletionOption.ResponseContentRead) {
+		public static Task<HttpResponseMessage> PutAsync(this IFlurlClient client, HttpContent content, CancellationToken cancellationToken = default(CancellationToken), HttpCompletionOption completionOption = HttpCompletionOption.ResponseContentRead) {
 			return client.SendAsync(HttpMethod.Put, content: content, cancellationToken: cancellationToken, completionOption: completionOption);
 		}
 
@@ -610,12 +610,12 @@ public static class HttpExtensions
 		/// <summary>
 		/// Sends an asynchronous PUT request.
 		/// </summary>
-		/// <param name="client">The Flurl client.</param>
+		/// <param name="client">The IFlurlClient instance.</param>
 		/// <param name="data">Contents of the request body.</param>
 		/// <param name="cancellationToken">A cancellation token that can be used by other objects or threads to receive notice of cancellation. Optional.</param>
 		/// <param name="completionOption">The HttpCompletionOption used in the request. Optional.</param>
 		/// <returns>A Task whose result is the received HttpResponseMessage.</returns>
-		public static Task<HttpResponseMessage> PutJsonAsync(this FlurlClient client, object data, CancellationToken cancellationToken = default(CancellationToken), HttpCompletionOption completionOption = HttpCompletionOption.ResponseContentRead) {
+		public static Task<HttpResponseMessage> PutJsonAsync(this IFlurlClient client, object data, CancellationToken cancellationToken = default(CancellationToken), HttpCompletionOption completionOption = HttpCompletionOption.ResponseContentRead) {
 			var content = new CapturedJsonContent(client.Settings.JsonSerializer.Serialize(data));
 			return client.SendAsync(HttpMethod.Put, content: content, cancellationToken: cancellationToken, completionOption: completionOption);
 		}
@@ -647,12 +647,12 @@ public static class HttpExtensions
 		/// <summary>
 		/// Sends an asynchronous PUT request.
 		/// </summary>
-		/// <param name="client">The Flurl client.</param>
+		/// <param name="client">The IFlurlClient instance.</param>
 		/// <param name="data">Contents of the request body.</param>
 		/// <param name="cancellationToken">A cancellation token that can be used by other objects or threads to receive notice of cancellation. Optional.</param>
 		/// <param name="completionOption">The HttpCompletionOption used in the request. Optional.</param>
 		/// <returns>A Task whose result is the received HttpResponseMessage.</returns>
-		public static Task<HttpResponseMessage> PutStringAsync(this FlurlClient client, string data, CancellationToken cancellationToken = default(CancellationToken), HttpCompletionOption completionOption = HttpCompletionOption.ResponseContentRead) {
+		public static Task<HttpResponseMessage> PutStringAsync(this IFlurlClient client, string data, CancellationToken cancellationToken = default(CancellationToken), HttpCompletionOption completionOption = HttpCompletionOption.ResponseContentRead) {
 			var content = new CapturedStringContent(data);
 			return client.SendAsync(HttpMethod.Put, content: content, cancellationToken: cancellationToken, completionOption: completionOption);
 		}
@@ -684,11 +684,11 @@ public static class HttpExtensions
 		/// <summary>
 		/// Sends an asynchronous DELETE request.
 		/// </summary>
-		/// <param name="client">The Flurl client.</param>
+		/// <param name="client">The IFlurlClient instance.</param>
 		/// <param name="cancellationToken">A cancellation token that can be used by other objects or threads to receive notice of cancellation. Optional.</param>
 		/// <param name="completionOption">The HttpCompletionOption used in the request. Optional.</param>
 		/// <returns>A Task whose result is the received HttpResponseMessage.</returns>
-		public static Task<HttpResponseMessage> DeleteAsync(this FlurlClient client, CancellationToken cancellationToken = default(CancellationToken), HttpCompletionOption completionOption = HttpCompletionOption.ResponseContentRead) {
+		public static Task<HttpResponseMessage> DeleteAsync(this IFlurlClient client, CancellationToken cancellationToken = default(CancellationToken), HttpCompletionOption completionOption = HttpCompletionOption.ResponseContentRead) {
 			return client.SendAsync(HttpMethod.Delete, cancellationToken: cancellationToken, completionOption: completionOption);
 		}
 
@@ -717,12 +717,12 @@ public static class HttpExtensions
 		/// <summary>
 		/// Sends an asynchronous PATCH request.
 		/// </summary>
-		/// <param name="client">The Flurl client.</param>
+		/// <param name="client">The IFlurlClient instance.</param>
 		/// <param name="content">Contents of the request body.</param>
 		/// <param name="cancellationToken">A cancellation token that can be used by other objects or threads to receive notice of cancellation. Optional.</param>
 		/// <param name="completionOption">The HttpCompletionOption used in the request. Optional.</param>
 		/// <returns>A Task whose result is the received HttpResponseMessage.</returns>
-		public static Task<HttpResponseMessage> PatchAsync(this FlurlClient client, HttpContent content, CancellationToken cancellationToken = default(CancellationToken), HttpCompletionOption completionOption = HttpCompletionOption.ResponseContentRead) {
+		public static Task<HttpResponseMessage> PatchAsync(this IFlurlClient client, HttpContent content, CancellationToken cancellationToken = default(CancellationToken), HttpCompletionOption completionOption = HttpCompletionOption.ResponseContentRead) {
 			return client.SendAsync(new HttpMethod("PATCH"), content: content, cancellationToken: cancellationToken, completionOption: completionOption);
 		}
 
@@ -753,12 +753,12 @@ public static class HttpExtensions
 		/// <summary>
 		/// Sends an asynchronous PATCH request.
 		/// </summary>
-		/// <param name="client">The Flurl client.</param>
+		/// <param name="client">The IFlurlClient instance.</param>
 		/// <param name="data">Contents of the request body.</param>
 		/// <param name="cancellationToken">A cancellation token that can be used by other objects or threads to receive notice of cancellation. Optional.</param>
 		/// <param name="completionOption">The HttpCompletionOption used in the request. Optional.</param>
 		/// <returns>A Task whose result is the received HttpResponseMessage.</returns>
-		public static Task<HttpResponseMessage> PatchJsonAsync(this FlurlClient client, object data, CancellationToken cancellationToken = default(CancellationToken), HttpCompletionOption completionOption = HttpCompletionOption.ResponseContentRead) {
+		public static Task<HttpResponseMessage> PatchJsonAsync(this IFlurlClient client, object data, CancellationToken cancellationToken = default(CancellationToken), HttpCompletionOption completionOption = HttpCompletionOption.ResponseContentRead) {
 			var content = new CapturedJsonContent(client.Settings.JsonSerializer.Serialize(data));
 			return client.SendAsync(new HttpMethod("PATCH"), content: content, cancellationToken: cancellationToken, completionOption: completionOption);
 		}
@@ -790,12 +790,12 @@ public static class HttpExtensions
 		/// <summary>
 		/// Sends an asynchronous PATCH request.
 		/// </summary>
-		/// <param name="client">The Flurl client.</param>
+		/// <param name="client">The IFlurlClient instance.</param>
 		/// <param name="data">Contents of the request body.</param>
 		/// <param name="cancellationToken">A cancellation token that can be used by other objects or threads to receive notice of cancellation. Optional.</param>
 		/// <param name="completionOption">The HttpCompletionOption used in the request. Optional.</param>
 		/// <returns>A Task whose result is the received HttpResponseMessage.</returns>
-		public static Task<HttpResponseMessage> PatchStringAsync(this FlurlClient client, string data, CancellationToken cancellationToken = default(CancellationToken), HttpCompletionOption completionOption = HttpCompletionOption.ResponseContentRead) {
+		public static Task<HttpResponseMessage> PatchStringAsync(this IFlurlClient client, string data, CancellationToken cancellationToken = default(CancellationToken), HttpCompletionOption completionOption = HttpCompletionOption.ResponseContentRead) {
 			var content = new CapturedStringContent(data);
 			return client.SendAsync(new HttpMethod("PATCH"), content: content, cancellationToken: cancellationToken, completionOption: completionOption);
 		}
diff --git a/src/Flurl.Http.Shared/MultipartExtensions.cs b/src/Flurl.Http.Shared/MultipartExtensions.cs
index 8703774c..ec05a6d0 100644
--- a/src/Flurl.Http.Shared/MultipartExtensions.cs
+++ b/src/Flurl.Http.Shared/MultipartExtensions.cs
@@ -18,7 +18,7 @@ public static class MultipartExtensions
 		/// <param name="client">The Flurl client.</param>
 		/// <param name="cancellationToken">A cancellation token that can be used by other objects or threads to receive notice of cancellation.</param>
 		/// <returns>A Task whose result is the received HttpResponseMessage.</returns>
-		public static Task<HttpResponseMessage> PostMultipartAsync(this FlurlClient client, Action<CapturedMultipartContent> buildContent, CancellationToken cancellationToken = default(CancellationToken)) {
+		public static Task<HttpResponseMessage> PostMultipartAsync(this IFlurlClient client, Action<CapturedMultipartContent> buildContent, CancellationToken cancellationToken = default(CancellationToken)) {
 			var cmc = new CapturedMultipartContent(client.Settings);
 			buildContent(cmc);
 			return client.SendAsync(HttpMethod.Post, cmc, cancellationToken);