How to use HTTP/2 in cURL

HTTP/2 improves web performance through multiplexing, header compression, and better resource management, reducing latency and enhancing user experience.

When interacting with servers that support HTTP/2, cURL can automatically negotiate this protocol, providing a way to confirm whether the server responds with multiplexed streams and potential performance gains over older protocols.

By verifying HTTP/2 support with cURL, developers can ensure endpoints are optimized for modern standards, enabling faster load times and improved network efficiency.

1. Open a terminal.
2. Request a URL and let cURL negotiate HTTP/2 automatically.

   $ curl --http2 "https://www.example.com"

   --http2 signals that cURL should attempt an HTTP/2 connection.

3. Use --verbose to confirm whether the connection upgraded to HTTP/2.

   $ curl --http2 --verbose "https://www.example.com" 2>&1 | grep 'Using HTTP2'

   Look for messages indicating HTTP/2 usage.

4. Compare performance with and without HTTP/2 to assess improvements.

   $ curl --http1.1 "https://www.example.com" --output old_protocol.txt
   $ curl --http2 "https://www.example.com" --output new_protocol.txt

   Compare transfer times or resource usage for insights into HTTP/2 benefits.

5. Confirm server HTTP/2 support before relying on it in production.

   If no HTTP/2 support, cURL falls back to HTTP/1.1.