HTTP/3 Testing with curl¶

For building curl with HTTP/3, see the official curl HTTP/3 documentation.

Verify HTTP/3 Support¶

curl -V
# Look for: Features: ... HTTP3 ...

Testing Commands¶

HTTP/3 GET¶

curl --http3 -k -sI https://localhost:4433/

Expected response:

HTTP/3 200
alt-svc: h3=":4433"; ma=60; persist=1

Verbose Handshake¶

curl --http3 -k -v https://localhost:4433/

Using HTTP/3 confirms a successful QUIC handshake.

Force HTTP/1.1 (TCP)¶

curl --http1.1 -k -sI https://localhost:4433/

Force HTTP/2 (TCP)¶

curl --http2 -k -sI https://localhost:4433/

HTTP/3 Only (Fail if No QUIC)¶

curl --http3-only -k -sI https://localhost:4433/

Unlike --http3, this does not fall back to HTTP/2 or HTTP/1.1. If the QUIC handshake fails, curl exits with an error.

Download a File¶

curl --http3 -k -o output.bin https://localhost:4433/pi

POST Data¶

curl --http3 -k -X POST -d "key=value" https://localhost:4433/api

PUT a File¶

curl --http3 -k -X PUT -T localfile.bin https://localhost:4433/upload/localfile.bin

Alt-Svc Header¶

mod_http3 injects Alt-Svc automatically when H3AltSvc is enabled, which is the default. Use mod_headers only to override that advertisement:

Header always set Alt-Svc "h3=\":4433\"; ma=60; persist=1"

Verify over HTTP/2 (TCP side):

curl --http2 -k -sI https://localhost:4433/

Built-in QUIC Client¶

The repo includes a native QUIC client (build/bin/quic_client_test) that connects to the standalone server (build/bin/server), not Apache httpd.

bash scripts/mkcert.sh keys
./build/bin/server 4433 keys/server.crt keys/server.key &
./build/bin/quic_client_test localhost 4433 keys/server.crt

Expected: Status 200, All streams complete.

Multiple concurrent streams:

./build/bin/quic_client_test localhost 4433 keys/server.crt 5

Common Failures¶