AspNetCore.Docs/aspnetcore/fundamentals/servers/kestrel.md

title	author	description	monikerRange	ms.author	ms.custom	ms.date	uid
Kestrel web server in ASP.NET Core	tdykstra	Learn about Kestrel, the cross-platform web server for ASP.NET Core.	>= aspnetcore-3.1	riande	mvc	04/04/2023	fundamentals/servers/kestrel

Kestrel web server in ASP.NET Core

By Tom Dykstra, Chris Ross, and Stephen Halter

:::moniker range=">= aspnetcore-8.0"

Kestrel is a cross-platform web server for ASP.NET Core. Kestrel is the recommended server for ASP.NET Core, and it's configured by default in ASP.NET Core project templates.

Kestrel's features include:

• Cross-platform: Kestrel is a cross-platform web server that runs on Windows, Linux, and macOS.
• High performance: Kestrel is optimized to handle a large number of concurrent connections efficiently.
• Lightweight: Optimized for running in resource-constrained environments, such as containers and edge devices.
• Security hardened: Kestrel supports HTTPS and is hardened against web server vulnerabilities.
• Wide protocol support: Kestrel supports common web protocols, including:
  • HTTP/1.1, HTTP/2 and HTTP/3
  • WebSockets
• Integration with ASP.NET Core: Seamless integration with other ASP.NET Core components, such as the middleware pipeline, dependency injection, and configuration system.
• Flexible workloads: Kestrel supports many workloads:
  • ASP.NET app frameworks such as Minimal APIs, MVC, Razor pages, SignalR, Blazor, and gRPC.
  • Building a reverse proxy with YARP.
• Extensibility: Customize Kestrel through configuration, middleware, and custom transports.
• Performance diagnostics: Kestrel provides built-in performance diagnostics features, such as logging and metrics.

Get started

ASP.NET Core project templates use Kestrel by default when not hosted with IIS. In the following template-generated Program.cs, the xref:Microsoft.AspNetCore.Builder.WebApplication.CreateBuilder%2A?displayProperty=nameWithType method calls xref:Microsoft.AspNetCore.Hosting.WebHostBuilderKestrelExtensions.UseKestrel%2A internally:

:::code language="csharp" source="~/fundamentals/servers/kestrel/samples/6.x/KestrelSample/Program.cs" id="snippet_CreateBuilder" highlight="1":::

For more information on configuring WebApplication and WebApplicationBuilder, see xref:fundamentals/minimal-apis.

Optional client certificates

For information on apps that must protect a subset of the app with a certificate, see Optional client certificates.

Behavior with debugger attached

The following timeouts and rate limits aren't enforced when a debugger is attached to a Kestrel process:

• xref:Microsoft.AspNetCore.Server.Kestrel.KestrelServerLimits.KeepAliveTimeout?displayProperty=nameWithType
• xref:Microsoft.AspNetCore.Server.Kestrel.KestrelServerLimits.RequestHeadersTimeout?displayProperty=nameWithType
• xref:Microsoft.AspNetCore.Server.Kestrel.Core.KestrelServerLimits.MinRequestBodyDataRate?displayProperty=nameWithType
• xref:Microsoft.AspNetCore.Server.Kestrel.Core.KestrelServerLimits.MinResponseDataRate?displayProperty=nameWithType
• xref:Microsoft.AspNetCore.Server.Kestrel.Core.Features.IConnectionTimeoutFeature
• xref:Microsoft.AspNetCore.Server.Kestrel.Core.Features.IHttpMinRequestBodyDataRateFeature
• xref:Microsoft.AspNetCore.Server.Kestrel.Core.Features.IHttpMinResponseDataRateFeature

Additional resources

• xref:fundamentals/servers/kestrel/endpoints
• Source for WebApplication.CreateBuilder method call to UseKestrel
• xref:fundamentals/servers/kestrel/options
• xref:fundamentals/servers/kestrel/http2
• xref:fundamentals/servers/kestrel/when-to-use-a-reverse-proxy
• xref:fundamentals/servers/kestrel/host-filtering
• xref:test/troubleshoot
• xref:security/enforcing-ssl
• xref:host-and-deploy/proxy-load-balancer
• RFC 9110: HTTP Semantics (Section 7.2: Host and :authority)
• When using UNIX sockets on Linux, the socket isn't automatically deleted on app shutdown. For more information, see this GitHub issue.

[!NOTE] As of ASP.NET Core 5.0, Kestrel's libuv transport is obsolete. The libuv transport doesn't receive updates to support new OS platforms, such as Windows ARM64, and will be removed in a future release. Remove any calls to the obsolete xref:Microsoft.AspNetCore.Hosting.WebHostBuilderLibuvExtensions.UseLibuv%2A method and use Kestrel's default Socket transport instead.

:::moniker-end

[!INCLUDE]