actix-web/guide/src/qs_13.md

# HTTP/2

Actix web automatically upgrades connection to *HTTP/2* if possible.

## Negotiation

*HTTP/2* protocol over tls without prior knowlage requires
[tls alpn](https://tools.ietf.org/html/rfc7301). At the moment only
`rust-openssl` has support. Turn on `alpn` feature to enable `alpn` negotiation.
With enable `alpn` feature `HttpServer` provides
[serve_tls](../actix_web/struct.HttpServer.html#method.serve_tls) method.

```toml
[dependencies]
actix-web = { git = "https://github.com/actix/actix-web", features=["alpn"] }
```

```rust,ignore
use std::fs::File;
use actix_web::*;

fn main() {
    let mut file = File::open("identity.pfx").unwrap();
    let mut pkcs12 = vec![];
    file.read_to_end(&mut pkcs12).unwrap();
    let pkcs12 = Pkcs12::from_der(&pkcs12).unwrap().parse("12345").unwrap();

    HttpServer::new(
        Application::default("/")
            .route("/index.html", |r| r.f(index))
        .serve_tls::<_, ()>("127.0.0.1:8080", pkcs12).unwrap();
}
```

Upgrade to *HTTP/2* schema described in
[rfc section 3.2](https://http2.github.io/http2-spec/#rfc.section.3.2) is not supported.
Starting *HTTP/2* with prior knowledge is supported for both clear text connection
and tls connection. [rfc section 3.4](https://http2.github.io/http2-spec/#rfc.section.3.4)

Please check [example](https://github.com/actix/actix-web/tree/master/examples/tls) 
for concrete example.