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Repair Windows errors before they cause bigger problemsFix Now →Fix the driver behind crashes, sound loss and screen glitchesFind Drivers →Clear out junk files and repair common Windows errorsFree Scan →To use Refit in client-side Blazor, define an interface with Refit’s HTTP attributes, register an HttpClient with the API’s base address, and register the interface with Refit’s HttpClientFactory integration. Inject that interface into a component or application service. Refit generates the HTTP implementation; it does not bypass browser CORS rules or provide an authentication system.
What Refit does in a Blazor app
Refit turns a REST API into a C# interface and generates the HttpClient implementation. Its maintainers describe support for HttpClientFactory, pluggable serializers, and a testing package. In a Blazor WebAssembly app, that lets your application call an API through typed methods instead of assembling each request by hand.
The browser still performs the network requests. Refit does not change the browser’s security model, make a server-only API reachable from the browser, or hide client code and request data from users.
Install Refit in the client project
Add the Refit package and its HttpClientFactory integration to the project that runs the client-side code. For a standalone WebAssembly app, that is usually the app project; for a Blazor Web App with a separate client project, use the .Client project.
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dotnet add package Refit --version 16.1.0
dotnet add package Refit.HttpClientFactory --version 16.1.0NuGet lists Refit 16.1.0 as updated on September 21, 2026, with package targets for .NET 8, 9, 10, and 11. Its package metadata says the source generator requires Roslyn 4.8 or newer. Check the package’s target-framework compatibility and your project’s compiler and deployment configuration before pinning a version; these package targets do not by themselves guarantee compatibility with every runtime configuration.
Define an interface for the API
Use Refit attributes to describe the HTTP method and route. Route values come from method parameters that match route placeholders; parameters not used in the route become query parameters. Mark a request payload with [Body].
using Refit;
public interface IGitHubApi
{
[Get("/users/{login}")]
Task<GitHubUser> GetUserAsync(string login);
[Get("/repos/{owner}/{repo}/issues")]
Task<IReadOnlyList<GitHubIssue>> GetIssuesAsync(
string owner,
string repo,
[AliasAs("state")] string? state = null);
[Post("/repos/{owner}/{repo}/issues")]
Task<GitHubIssue> CreateIssueAsync(
string owner,
string repo,
[Body] NewIssue issue);
}Define the response and request types to match the API’s JSON contract. The example uses GitHub-shaped routes to illustrate Refit syntax; replace them and the model types with the endpoints and payloads your API actually supports. For a query parameter, [AliasAs("state")] makes the wire name explicit rather than relying on a C# parameter name.
Register the API base address and Refit client
In Program.cs for the client project, register the interface with Refit’s HttpClientFactory integration and configure the base address:
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var builder = WebAssemblyHostBuilder.CreateDefault(args);
builder.Services
.AddRefitClient<IGitHubApi>()
.ConfigureHttpClient(client =>
{
client.BaseAddress = new Uri("https://api.github.com/");
});Keep the trailing slash on the base URI when API routes begin with a slash, as in the interface above. For a same-origin API, set the address to the application’s origin as appropriate. Microsoft’s client-side Blazor guidance shows a preconfigured HttpClient registered with builder.HostEnvironment.BaseAddress for that same-origin case; that app-origin address is not automatically the right base address for an external API.
Microsoft also documents named and typed HttpClient registration as supported client patterns in Blazor WebAssembly and .Client projects. Refit’s HttpClientFactory integration is a convenient fit when the interface should be created for a configured client. If using a different factory arrangement, make sure the Refit interface is built with the client configured for the intended API rather than an unrelated app-origin client.
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Inject the interface and call it asynchronously
A Razor component can inject the interface directly. Keep the component responsible for UI state and rendering; put reusable API workflows in an application service when multiple components need them.
@page "/users/{Login}"
@inject IGitHubApi GitHubApi
<h1>User</h1>
@if (Loading)
{
<p>Loading…</p>
}
else if (ErrorMessage is not null)
{
<p role="alert">@ErrorMessage</p>
}
else if (User is not null)
{
<p>@User.Name</p>
}
@code {
[Parameter]
public string Login { get; set; } = "";
private GitHubUser? User;
private bool Loading;
private string? ErrorMessage;
protected override async Task OnParametersSetAsync()
{
Loading = true;
ErrorMessage = null;
try
{
User = await GitHubApi.GetUserAsync(Login);
}
catch (ApiException ex)
{
ErrorMessage = $"The API returned HTTP {(int)ex.StatusCode}.";
}
catch (HttpRequestException)
{
ErrorMessage = "The request could not reach the API.";
}
finally
{
Loading = false;
}
}
}ApiException is useful for handling unsuccessful HTTP responses from a Refit call. Network failures, including browser-enforced CORS failures, can instead surface as transport exceptions; do not assume every failure will include a readable API response body. Applications should decide how to present validation errors, authorization failures, rate limits, and transient network problems for their own API.
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Account for CORS and browser authentication
If the API has a different origin from the Blazor app, the API must permit the browser request under its CORS policy. Configure the API for the app’s allowed origin and the required methods and headers; if the request uses credentials, the API’s CORS and credential settings must also be compatible with that browser request. Refit cannot relax or override these restrictions.
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For an authenticated API, use a browser-compatible sign-in and token flow and attach tokens to requests through the application’s supported request configuration. Never embed a client secret or other confidential credential in WebAssembly code: the deployed files and requests are observable by the user’s browser. Refit generates requests, but does not replace the app’s authentication and authorization design.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Handle prerendering in both service containers
In a Blazor Web App that prerenders client-side components, the server renders the component before the browser starts the WebAssembly client. If that component injects a Refit interface, the server-side service container also needs a matching registration; registering it only in the client project can cause dependency resolution to fail during prerendering.
Register the logical client in both the server project and the .Client project, using the same API base address and equivalent configuration where appropriate. The client-side registration still belongs in the client’s Program.cs; the server registration belongs in the server’s service setup. This is specifically a prerendering concern, not a requirement for a standalone WebAssembly app that has no server-side prerendering.
Check .NET 11 and Mono deployment compatibility
Refit’s breaking-change documentation warns that .NET 11 assemblies built with runtime-async can fail on Mono, including Blazor WebAssembly deployments that use Mono. The warning does not mean Refit is generally unsuitable for Blazor: it is a deployment-configuration compatibility check. Confirm whether the app uses Mono or opts into CoreCLR, and verify the selected Refit build against that runtime before deployment. The documentation also identifies WASI and other supported configurations in connection with this issue.
When Refit is a good fit
Refit is most useful when a team wants API calls expressed as a typed interface and wants to reduce handwritten request plumbing. Before choosing it, compare that benefit with the project’s API-contract workflow and its requirements for generated OpenAPI clients, serialization customization, trimming or AOT behavior, error handling, and testability. Handwritten HttpClient remains a supported Blazor option, and Microsoft documents named and typed clients as alternatives. Whichever approach you choose, configure the same base address, browser-compatible authentication, and error handling deliberately.
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