Keep-Alive

The Keep-Alive general header allows the sender to hint about how the connection 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.

Connection-specific header fields such as Connection and Keep-Alive are prohibited in HTTP/2. Chrome and Firefox ignore them in HTTP/2 responses, but Safari conforms to the HTTP/2 spec requirements and won’t load any response which contains them.

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 sent 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
HTTP Keep-Alive Header Keep-Alive Header (IETF Internet Draft)
RFC 7230, appendix A.1.2: Keep-Alive Hypertext Transfer Protocol (HTTP/1.1): Message Syntax and Routing

Browser compatibility

DesktopMobile
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidFirefox for AndroidOpera for AndroidSafari on iOSSamsung Internet
Keep-AliveChrome Full support YesEdge Full support 12Firefox Full support YesIE Full support YesOpera Full support YesSafari Full support YesWebView Android Full support YesChrome Android 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

See also