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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.

Header type	General header
Forbidden header name	no

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	Edge	Firefox	Internet Explorer	Opera	Safari
Basic support	Yes	Yes	Yes	Yes	Yes	Yes