1<!-- 2Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al. 3 4SPDX-License-Identifier: curl 5--> 6 7# Experimental 8 9Some features and functionality in curl and libcurl are considered 10**EXPERIMENTAL**. 11 12Experimental support in curl means: 13 141. Experimental features are provided to allow users to try them out and 15 provide feedback on functionality and API etc before they ship and get 16 "carved in stone". 172. You must enable the feature when invoking configure as otherwise curl is 18 not built with the feature present. 193. We strongly advise against using this feature in production. 204. **We reserve the right to change behavior** of the feature without sticking 21 to our API/ABI rules as we do for regular features, as long as it is marked 22 experimental. 235. Experimental features are clearly marked so in documentation. Beware. 24 25## Graduation 26 271. Each experimental feature should have a set of documented requirements of 28 what is needed for that feature to graduate. Graduation means being removed 29 from the list of experiments. 302. An experiment should NOT graduate if it needs test cases to be disabled, 31 unless they are for minor features that are clearly documented as not 32 provided by the experiment and then the disabling should be managed inside 33 each affected test case. 34 35## Experimental features right now 36 37### The Hyper HTTP backend 38 39Graduation requirements: 40 41- HTTP/1 and HTTP/2 support, including multiplexing 42 43(Hyper is marked for deprecation. It cannot graduate.) 44 45### HTTP/3 support (non-ngtcp2 backends) 46 47Graduation requirements: 48 49- The used libraries should be considered out-of-beta with a reasonable 50 expectation of a stable API going forward. 51 52- Using HTTP/3 with the given build should perform without risking busy-loops 53 54### The Rustls backend 55 56Graduation requirements: 57 58- a reasonable expectation of a stable API going forward. 59 60## ECH 61 62Use of the HTTPS resource record and Encrypted Client Hello (ECH) when using 63DoH 64 65Graduation requirements: 66 67- ECH support exists in at least one widely used TLS library apart from 68 BoringSSL and wolfSSL. 69 70- feedback from users saying that ECH works for their use cases 71 72- it has been given time to mature, so no earlier than April 2025 (twelve 73 months after being added here) 74
