Servers - Kestrel - HTTP/3

In this article

Important Apps configured to take advantage of HTTP/3 should be designed to also support HTTP/1.1 and HTTP/2.

HTTP/3 requirements

Windows

• Windows 11 Build 22000 or later OR Windows Server 2022.

• TLS 1.3 or later connection.

Linux

• libmsquic package installed.

• Add the packages.microsoft.com repository. See Linux Software Repository for Microsoft Products for instructions.

• Install the libmsquic package using the distro's package manager. For example, apt install libmsquic=1.9* on Ubuntu.

macOS

Getting started

var builder = WebApplication.CreateBuilder(args);

builder.WebHost.ConfigureKestrel((context, options) =>
{
    options.ListenAnyIP(5001, listenOptions =>
    {
        listenOptions.Protocols = HttpProtocols.Http1AndHttp2AndHttp3;
        listenOptions.UseHttps();
    });
});

• Use HTTP/3 alongside HTTP/1.1 and HTTP/2 by specifying HttpProtocols.Http1AndHttp2AndHttp3.

• Enable HTTPS with UseHttps. HTTP/3 requires HTTPS.

Alt-svc

Localhost testing

• Browsers don't allow self-signed certificates on HTTP/3, such as the Kestrel development certificate.

• HttpClient can be used for localhost/loopback testing in .NET 6 or later. Extra configuration is required when using HttpClient to make an HTTP/3 request:

  • Set HttpRequestMessage.Version to 3.0, or

  • Set HttpRequestMessage.VersionPolicy to HttpVersionPolicy.RequestVersionOrHigher.

HTTP/3 benefits

• Faster response time of the first request. QUIC and HTTP/3 negotiates the connection in fewer round-trips between the client and the server. The first request reaches the server faster.

• Improved experience when there is connection packet loss. HTTP/2 multiplexes multiple requests via one TCP connection. Packet loss on the connection affects all requests. This problem is called "head-of-line blocking". Because QUIC provides native multiplexing, lost packets only impact the requests where data has been lost.

• Supports transitioning between networks. This feature is useful for mobile devices where it is common to switch between WIFI and cellular networks as a mobile device changes location. Currently, HTTP/1.1 and HTTP/2 connections fail with an error when switching networks. An app or web browsers must retry any failed HTTP requests. HTTP/3 allows the app or web browser to seamlessly continue when a network changes. Kestrel doesn't support network transitions in .NET 8. It may be available in a future release.

Ref: Use HTTP/3 with the ASP.NET Core Kestrel web server