1---
2c: Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
3SPDX-License-Identifier: curl
4Long: http2-prior-knowledge
5Tags: Versions
6Protocols: HTTP
7Added: 7.49.0
8Mutexed: http1.1 http1.0 http2 http3
9Requires: HTTP/2
10Help: Use HTTP 2 without HTTP/1.1 Upgrade
11Category: http
12Multi: boolean
13See-also:
14  - http2
15  - http3
16Example:
17  - --http2-prior-knowledge $URL
18---
19
20# `--http2-prior-knowledge`
21
22Issue a non-TLS HTTP requests using HTTP/2 directly without HTTP/1.1 Upgrade.
23It requires prior knowledge that the server supports HTTP/2 straight away.
24HTTPS requests still do HTTP/2 the standard way with negotiated protocol
25version in the TLS handshake.
26
27Since 8.10.0 if this option is set for an HTTPS request then the application
28layer protocol version (ALPN) offered to the server is only HTTP/2. Prior to
29that both HTTP/1.1 and HTTP/2 were offered.
30