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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 yes

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, appendix A.1.2: Keep-Alive Hypertext Transfer Protocol (HTTP/1.1): Message Syntax and Routing
RFC 2068, section 19.7.1.1: The Keep-Alive Header Hypertext Transfer Protocol -- HTTP/1.1

Browser compatibility

Update compatibility data on GitHub
DesktopMobile
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidEdge MobileFirefox for AndroidOpera for AndroidiOS SafariSamsung Internet
Basic support
ExperimentalDeprecatedNon-standard
Chrome Full support YesEdge Full support YesFirefox Full support YesIE Full support YesOpera Full support YesSafari Full support YesWebView Android Full support YesChrome Android Full support YesEdge Mobile Full support YesFirefox Android Full support YesOpera Android Full support YesSafari iOS Full support YesSamsung Internet Android Full support Yes

Legend

Full support  
Full support
Experimental. Expect behavior to change in the future.
Experimental. Expect behavior to change in the future.
Non-standard. Expect poor cross-browser support.
Non-standard. Expect poor cross-browser support.
Deprecated. Not for use in new websites.
Deprecated. Not for use in new websites.

See also

Метки документа и участники

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