# Experimental Some features and functionality in curl and libcurl are considered **EXPERIMENTAL**. Experimental support in curl means: 1. Experimental features are provided to allow users to try them out and provide feedback on functionality and API etc before they ship and get "carved in stone". 2. You must enable the feature when invoking configure as otherwise curl is not built with the feature present. 3. We strongly advise against using this feature in production. 4. **We reserve the right to change behavior** of the feature without sticking to our API/ABI rules as we do for regular features, as long as it is marked experimental. 5. Experimental features are clearly marked so in documentation. Beware. ## Experimental features right now - The Hyper HTTP backend - HTTP/3 support (using the quiche or msh3 backends) - The rustls backend - WebSocket - Use of the HTTPS resource record and Encrypted Client Hello (ECH) when using DoH