1# Alt-Svc 2 3curl features **EXPERIMENTAL** support for the Alt-Svc: HTTP header. 4 5## Enable Alt-Svc in build 6 7`./configure --enable-alt-svc` 8 9## Standard 10 11[RFC 7838](https://tools.ietf.org/html/rfc7838) 12 13# Alt-Svc cache file format 14 15This a text based file with one line per entry and each line consists of nine 16space separated fields. 17 18## Example 19 20 h2 quic.tech 8443 h3-22 quic.tech 8443 "20190808 06:18:37" 0 0 21 22## Fields 23 241. The ALPN id for the source origin 252. The host name for the source origin 263. The port number for the source origin 274. The ALPN id for the destination host 285. The host name for the destination host 296. The host number for the destination host 307. The expiration date and time of this entry within double quotes. The date format is "YYYYMMDD HH:MM:SS" and the time zone is GMT. 318. Boolean (1 or 0) if "persist" was set for this entry 329. Integer priority value (not currently used) 33 34# TODO 35 36- handle multiple response headers, when one of them says `clear` (should 37 override them all) 38- using `Age:` value for caching age as per spec 39- `CURLALTSVC_IMMEDIATELY` support 40