curl/docs/cmdline-opts/http3-only.md

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c: Copyright (C) Daniel Stenberg, daniel@haxx.se, et al. SPDX-License-Identifier: curl Long: http3-only Tags: Versions Protocols: HTTP Added: 7.88.0 Mutexed: http1.1 http1.0 http2 http2-prior-knowledge http3 Requires: HTTP/3 Help: Use HTTP v3 only Category: http Multi: mutex See-also:

• http1.1
• http2
• http3 Example:
• --http3-only $URL ---

--http3-only

Instructs curl to use HTTP/3 to the host in the URL, with no fallback to earlier HTTP versions. HTTP/3 can only be used for HTTPS and not for HTTP URLs. For HTTP, this option triggers an error.

This option allows a user to avoid using the Alt-Svc method of upgrading to HTTP/3 when you know that the target speaks HTTP/3 on the given host and port.

This option makes curl fail if a QUIC connection cannot be established, it does not attempt any other HTTP versions on its own. Use --http3 for similar functionality with a fallback.