1--- 2c: Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al. 3SPDX-License-Identifier: curl 4Long: http3 5Tags: Versions 6Protocols: HTTP 7Added: 7.66.0 8Mutexed: http1.1 http1.0 http2 http2-prior-knowledge http3-only 9Requires: HTTP/3 10Help: Use HTTP v3 11Category: http 12Multi: mutex 13See-also: 14 - http1.1 15 - http2 16Example: 17 - --http3 $URL 18--- 19 20# `--http3` 21 22Attempt HTTP/3 to the host in the URL, but fallback to earlier HTTP versions 23if the HTTP/3 connection establishment fails or is slow. HTTP/3 is only 24available for HTTPS and not for HTTP URLs. 25 26This option allows a user to avoid using the Alt-Svc method of upgrading to 27HTTP/3 when you know or suspect that the target speaks HTTP/3 on the given 28host and port. 29 30When asked to use HTTP/3, curl issues a separate attempt to use older HTTP 31versions with a slight delay, so if the HTTP/3 transfer fails or is slow, curl 32still tries to proceed with an older HTTP version. The fallback performs the 33regular negotiation between HTTP/1 and HTTP/2. 34 35Use --http3-only for similar functionality *without* a fallback. 36
