C# HTTP Client Libraries Compared: RestSharp vs Refit vs HttpClientFactory — Which One Should You Use in 2026?

Introduction

Making HTTP calls is one of the most fundamental operations in modern application development. Whether you’re consuming REST APIs, downloading files, or communicating with microservices, your choice of HTTP client library has a direct impact on your code’s readability, maintainability, and performance. In the .NET ecosystem, three options stand out: RestSharp, Refit, and the built-in HttpClientFactory. Each takes a fundamentally different approach to HTTP communication, and choosing the wrong one can lead to verbose, error-prone code — or worse, socket exhaustion under load.

In this guide, we compare RestSharp (9,829 GitHub stars), Refit (9,556 stars), and Microsoft’s HttpClientFactory to help you pick the right tool for your next .NET project.

Comparison Table

RestSharp: The Fluent Workhorse

RestSharp has been the go-to HTTP client for .NET developers since 2009. It wraps HttpClient with a fluent, easy-to-use API that handles serialization, deserialization, authentication, and parameter building out of the box.

Installation

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dotnet add package RestSharp

Basic Usage

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using RestSharp;

var client = new RestClient("https://api.example.com");
var request = new RestRequest("/users/{id}", Method.Get);
request.AddUrlSegment("id", 42);
request.AddHeader("Authorization", "Bearer token123");

var response = await client.ExecuteAsync<User>(request);

if (response.IsSuccessful)
{
    var user = response.Data;
    Console.WriteLine($"User: {user.Name}");
}

RestSharp shines when you need quick, readable HTTP calls without ceremony. Its ExecuteAsync<T>() method handles JSON deserialization automatically using its built-in serializer. For POST requests, you simply call request.AddJsonBody(payload).

Authentication Support

RestSharp provides built-in authenticators for common scenarios:

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// OAuth2
client.AddDefaultHeader("Authorization", $"Bearer {token}");

// Basic Auth
client.Authenticator = new HttpBasicAuthenticator("username", "password");

// JWT
client.Authenticator = new JwtAuthenticator(jwtToken);

Error Handling

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var response = await client.ExecuteAsync(request);

if (!response.IsSuccessful)
{
    Console.WriteLine($"Error: {response.StatusCode} - {response.ErrorMessage}");
    if (response.ErrorException != null)
        throw response.ErrorException;
}

Refit: Interface-Driven Type Safety

Refit takes a radically different approach: you define your API as a C# interface decorated with attributes, and Refit generates the implementation at runtime. This declarative style eliminates boilerplate HTTP code and catches endpoint mismatches at compile time.

Installation

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dotnet add package Refit
dotnet add package Refit.HttpClientFactory

Basic Usage

Define your API contract as an interface:

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using Refit;

public interface IGitHubApi
{
    [Get("/users/{username}")]
    Task<User> GetUserAsync(string username);

    [Post("/repos/{owner}/{repo}/issues")]
    Task<Issue> CreateIssueAsync(string owner, string repo, [Body] CreateIssueRequest request);
}

Register with dependency injection:

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// Program.cs
builder.Services
    .AddRefitClient<IGitHubApi>()
    .ConfigureHttpClient(c => c.BaseAddress = new Uri("https://api.github.com"));

Then inject and use:

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public class GitHubService
{
    private readonly IGitHubApi _api;

    public GitHubService(IGitHubApi api) => _api = api;

    public async Task<User> GetUser(string username)
        => await _api.GetUserAsync(username);
}

Advanced Configuration

Refit integrates seamlessly with IHttpClientBuilder for resilience policies:

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builder.Services
    .AddRefitClient<IGitHubApi>()
    .ConfigureHttpClient(c =>
    {
        c.BaseAddress = new Uri("https://api.github.com");
        c.DefaultRequestHeaders.UserAgent.ParseAdd("MyApp/1.0");
        c.Timeout = TimeSpan.FromSeconds(30);
    })
    .AddTransientHttpErrorPolicy(p =>
        p.WaitAndRetryAsync(3, retryAttempt =>
            TimeSpan.FromSeconds(Math.Pow(2, retryAttempt))));

Content Serialization

Refit supports pluggable serializers:

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builder.Services
    .AddRefitClient<IMyApi>(new RefitSettings
    {
        ContentSerializer = new SystemTextJsonContentSerializer(
            new JsonSerializerOptions { PropertyNamingPolicy = JsonNamingPolicy.SnakeCaseLower })
    });

HttpClientFactory: The Foundation

HttpClientFactory isn’t a high-level HTTP library — it’s Microsoft’s solution to the infamous HttpClient socket exhaustion problem. Before IHttpClientFactory, developers commonly created new HttpClient instances per request, which leaked sockets under load. The factory manages the underlying HttpMessageHandler pool, keeping connections alive and preventing port exhaustion.

Installation

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dotnet add package Microsoft.Extensions.Http

Named Clients

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// Program.cs
builder.Services.AddHttpClient("GitHub", client =>
{
    client.BaseAddress = new Uri("https://api.github.com");
    client.DefaultRequestHeaders.Add("Accept", "application/vnd.github.v3+json");
    client.DefaultRequestHeaders.UserAgent.ParseAdd("MyApp/1.0");
    client.Timeout = TimeSpan.FromSeconds(30);
});

Typed Clients

The preferred pattern wraps an HttpClient in a service class:

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public class GitHubClient
{
    private readonly HttpClient _http;

    public GitHubClient(HttpClient http) => _http = http;

    public async Task<User?> GetUserAsync(string username)
    {
        var response = await _http.GetAsync($"/users/{username}");
        response.EnsureSuccessStatusCode();
        return await response.Content.ReadFromJsonAsync<User>();
    }
}

// Registration
builder.Services.AddHttpClient<GitHubClient>(c =>
    c.BaseAddress = new Uri("https://api.github.com"));

Adding Polly Resilience

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builder.Services.AddHttpClient<GitHubClient>(c =>
    c.BaseAddress = new Uri("https://api.github.com"))
    .AddTransientHttpErrorPolicy(p =>
        p.CircuitBreakerAsync(5, TimeSpan.FromSeconds(30)));

When to Use Which

Why Consider Your HTTP Client Strategy

Choosing the right HTTP client is more than a matter of syntax preference — it affects your application’s reliability, testability, and long-term maintainability. A well-designed HTTP layer handles transient failures gracefully, prevents socket exhaustion, and makes API integration tests straightforward. For more on C# dependency injection patterns that complement HTTP client registration, see our C# DI containers comparison. If you’re also working with API response serialization, our C# serialization libraries guide covers the serializers these HTTP clients use under the hood. For testing your HTTP integration, check out our C# testing frameworks comparison.

Migration Strategies: Moving Between HTTP Client Approaches

Switching HTTP client libraries mid-project is a common scenario as requirements evolve. Here’s how to approach each migration path without disrupting your application.

From raw HttpClient to RestSharp is the easiest transition — RestSharp wraps HttpClient internally, so your existing handler configurations and Polly policies remain compatible. Start by replacing individual endpoint calls one at a time, keeping your DI registrations intact. RestSharp’s fluent API typically reduces HTTP-related code by 40-60%.

From HttpClientFactory to Refit offers the biggest productivity gain for API-heavy projects. Since Refit integrates with IHttpClientBuilder, your existing resilience policies, base addresses, and timeout configurations carry over seamlessly. Begin with the most complex endpoints — Refit’s compile-time type checking catches parameter errors that manual HttpClient code would only reveal at runtime.

From RestSharp to Refit is worthwhile when you have a well-defined API contract with many endpoints. The main effort is defining the interface — each RestRequest maps to a Refit method attribute. Unlike RestSharp’s runtime configuration, Refit validates endpoint paths at compile time, catching typos in URL patterns before deployment.

For teams running CI/CD pipelines, a gradual migration with feature flags works best: register both clients side-by-side, route traffic progressively, and remove the old client once all calls have been migrated and verified in production.

FAQ

Can I use Refit and HttpClientFactory together?

Yes — this is the recommended pattern. AddRefitClient<T>() returns an IHttpClientBuilder, so you can chain Polly policies, configure the primary HttpMessageHandler, or add delegating handlers exactly as you would with a named or typed client.

Does RestSharp support .NET 8 and 9?

Yes. RestSharp v112+ fully supports .NET 8 and .NET 9, including native AOT compilation with appropriate configuration. Check the project’s GitHub releases for the latest target framework support.

How do I mock HTTP calls for unit testing?

With Refit, you mock the generated interface directly using your preferred mocking framework (Moq, NSubstitute, etc.). For HttpClientFactory, inject a custom HttpMessageHandler stub that returns predefined responses. RestSharp v112+ includes a test-friendly RestClient constructor that accepts a custom HttpMessageHandler.

What about gRPC and WebSocket connections?

None of these libraries support gRPC or WebSocket communication. For gRPC, use Grpc.Net.Client. For WebSocket, use ClientWebSocket from the System.Net.WebSockets namespace. These are entirely different protocols that require specialized clients.

Which library handles rate limiting best?

None provide built-in rate limiting, but all three integrate cleanly with Polly. You can add a RateLimitAsync policy via Microsoft.Extensions.Http.Resilience (the modern replacement for Microsoft.Extensions.Http.Polly) that applies to any client configured through IHttpClientBuilder.

How do these compare to using raw HttpClient directly?

Raw HttpClient requires manual JSON serialization, URL construction, query string building, header management, and error handling — all of which RestSharp and Refit handle automatically. The key benefit of HttpClientFactory over raw new HttpClient() is automatic HttpMessageHandler lifecycle management, which prevents the socket exhaustion problem that plagued .NET applications for years.

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