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Keep-Alive

Non-standard
This feature is non-standard and is not on a standards track. Do not use it on production sites facing the Web: it will not work for every user. There may also be large incompatibilities between implementations and the behavior may change in the future.

The Keep-Alive general header allows the sender to hint about how the connection and may be used to set a timeout and a maximum amount of requests.

The Connection header needs to be set to "keep-alive" for this header to have any meaning. Also, Connection and Keep-Alive are ignored in HTTP/2; connection management is handled by other mechanisms there.

Syntax

Keep-Alive: parameters

Directives

parameters
A comma-separated list of parameters, each consisting of an identifier and a value separated by the equal sign ('='). The following identifiers are possible:
  • timeout: indicating the minimum amount of time an idle connection has to be kept opened (in seconds). Note that timeouts longer than the TCP timeout may be ignored if no keep-alive TCP message is set at the transport level.
  • max: indicating the maximum number of requests that can be sent on this connection before closing it. Unless 0, this value is ignored for non-pipelined connections as another request will be send in the next response. An HTTP pipeline can use it to limit the pipelining.

Examples

A response containing a Keep-Alive header:

HTTP/1.1 200 OK
Connection: Keep-Alive
Content-Encoding: gzip
Content-Type: text/html; charset=utf-8
Date: Thu, 11 Aug 2016 15:23:13 GMT
Keep-Alive: timeout=5, max=1000
Last-Modified: Mon, 25 Jul 2016 04:32:39 GMT
Server: Apache

(body)

Specifications

Specification Title
HyperText Transport Protocol Keep-Alive Header The Keep-Alive Header (Experimental specification)
RFC 7230, section appendix-A.1.2: Keep-Alive Hypertext Transfer Protocol (HTTP/1.1): Message Syntax and Routing

Browser compatibility

Feature Chrome Firefox Edge Internet Explorer Opera Safari
Basic Support (Yes) (Yes) (Yes) (Yes) (Yes) (Yes)
Feature Android Chrome for Android Edge mobile Firefox for Android IE mobile Opera Android iOS Safari
Basic Support (Yes) (Yes) (Yes) (Yes) (Yes) (Yes) (Yes)

See also

© 2005–2017 Mozilla Developer Network and individual contributors.
Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.
https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Keep-Alive