cURL by Example: HTTP/3 Request
Force the use of HTTP/3 (QUIC). Requires a cURL build with HTTP/3 support.
Code
# Force HTTP/3
curl --http3 https://google.com
# Fallback options
curl --http3-only https://example.comExplanation
HTTP/3 represents a major shift in how web traffic works. It runs over QUIC protocol using UDP instead of TCP, which enables faster connections and better performance on unreliable networks.
Benefits of HTTP/3 and QUIC:
- Faster connection establishment with 0-RTT resumption
- Better performance on lossy networks (mobile, WiFi)
- No head-of-line blocking at the transport layer
- Connection migration when switching networks
- Built-in encryption (no unencrypted HTTP/3)
HTTP/3 support in cURL is still maturing. You need a special build with QUIC library support like quiche, ngtcp2, or msh3. Standard cURL packages often don't include HTTP/3 because the libraries are newer and less stable.
To check if your cURL supports HTTP/3, run curl -V and look for HTTP3 in the features line. If it's not there, you'll need to compile cURL yourself or find a pre-built version with QUIC support.
Not all servers support HTTP/3 yet. Google, Cloudflare, and Facebook use it, but many websites still only support HTTP/2 or HTTP/1.1. The --http3 flag will fail if the server doesn't advertise HTTP/3 support.
Code Breakdown
--http3 attempts to use HTTP/3.curl -V to see if HTTP/3 is supported in your build.