Alt-Svc

Draft
This page is not complete.

This page needs to be completed by someone with a deeper understanding of HTTP Alternative Services than me. —ExE-Boss

The Alt-Svc header is used to list alternate ways to reach this website.

Syntax

Alt-Svc: clear
Alt-Svc: <service-list>; ma=<max-age>
Alt-Svc: <service-list>; ma=<max-age>; persist=1

<service-list>: Comma separated list of service definitions in the format of <service-name>="<host-name>:<port-number>", where <service-name> is a valid ALPN identifier.
<max-age>Optional: The time in seconds for which the alternative service is considered valid for establishing new connections. Defaults to 24 hours.
persistOptional: Optional parameter specifying that the alternative service can be remembered between sessions and network changes.

Specification	Status	Comment
RFC 7838	IETF RFC	Initial definition.

	Desktop						Mobile
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet
`Alt-Svc`	Chrome Full support Yes	Edge ?	Firefox Full support 38 Full support 38 No support 37 — 38 Notes Notes Only supports draft-04 No support 35 — 37 Notes Disabled Notes Only supports draft-03 Disabled From version 35 until version 37 (exclusive): this feature is behind the `network.http.altsvc.enabled` preference (needs to be set to `true`) and the `altsvc.oe` preference (needs to be set to `true`). To change preferences in Firefox, visit about:config.	IE ?	Opera Full support Yes	Safari ?	WebView Android Full support Yes	Chrome Android Full support Yes	Firefox Android Full support 38 Full support 38 No support 37 — 38 Notes Notes Only supports draft-04 No support 35 — 37 Notes Disabled Notes Only supports draft-03 Disabled From version 35 until version 37 (exclusive): this feature is behind the `network.http.altsvc.enabled` preference (needs to be set to `true`) and the `altsvc.oe` preference (needs to be set to `true`). To change preferences in Firefox, visit about:config.	Opera Android Full support Yes	Safari iOS ?	Samsung Internet Android Full support Yes

Full support: Full support
Compatibility unknown: Compatibility unknown
See implementation notes.: See implementation notes.
User must explicitly enable this feature.: User must explicitly enable this feature.