HTTP/2 request

Force HTTP/2 and check protocol in response

curl --http2 -sI https://example.com | grep -i 'http\|alt-svc'

More curl commands

Set custom DNS resolver

curl --resolve example.com:443:1.2.3.4 https://example.com

Override DNS for a host:port pair (test behind CDN/LB)
Retry on failure

curl --retry 5 --retry-delay 2 --retry-all-errors https://api.example.com/healthz

Retry up to 5 times with 2s delay on any error
POST form data

curl -d 'user=alice&pass=secret' -X POST https://auth.example.com/login

Send URL-encoded form data
Client certificate auth

curl --cert client.crt --key client.key --cacert ca.crt https://secure.example.com

mTLS request with client cert and custom CA
Parallel downloads with xargs

cat urls.txt | xargs -P 5 -I{} curl -sSL -o /dev/null -w '%{url_effective} %{http_code}\n' {}

Download 5 URLs in parallel and print status codes