topic
Verified 2026-09-18Alt-Svc and Protocol Discovery
Alt-Svc advertises an alternative service where a resource can be reached.
Use Alt-Svc to advertise HTTP/2, HTTP/3, or another compatible endpoint. The client can switch after validating the alternative service.
httphttp2http3performance
Reference (http)
Alt-Svc: h3=":443"; ma=86400 Alt-Used: example.com
Use Alt-Svc to advertise HTTP/2, HTTP/3, or another compatible endpoint. The client can switch after validating the alternative service.
Common mistakes
- Advertising an alternative origin without considering certificate identity, authority, and cache lifetime.
Sources