actix-website/docs/http2.md

---
title: HTTP/2
---

import RenderCodeBlock from '@theme/CodeBlock';
import CodeBlock from '@site/src/components/code_block';

`actix-web` automatically upgrades connections to _HTTP/2_ if possible.

# Negotiation

<!-- TODO: use rustls example -->

When either of the `rustls` or `openssl` features are enabled, `HttpServer` provides the [`bind_rustls()`][bindrustls] method and [`bind_openssl()`][bindopenssl] methods, respectively.

<!-- DEPENDENCY -->

<CodeBlock example="http2" file="manifest" section="deps" language="toml"></CodeBlock>

<CodeBlock example="http2" file="main.rs" section="main" />

Upgrades to HTTP/2 described in [RFC 7540 §3.2][rfcsection32] are not supported. Starting HTTP/2 with prior knowledge is supported for both cleartext and TLS connections ([RFC 7540 §3.4][rfcsection34]) (when using the lower level `actix-http` service builders).

> Check out [the TLS examples][examples] for concrete example.

[rfcsection32]: https://httpwg.org/specs/rfc7540.html#rfc.section.3.2
[rfcsection34]: https://httpwg.org/specs/rfc7540.html#rfc.section.3.4
[bindrustls]: https://docs.rs/actix-web/4/actix_web/struct.HttpServer.html#method.bind_rustls_0_22
[bindopenssl]: https://docs.rs/actix-web/4/actix_web/struct.HttpServer.html#method.bind_openssl
[tlsalpn]: https://tools.ietf.org/html/rfc7301
[examples]: https://github.com/actix/examples/tree/master/https-tls