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 Request header, Response 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
Hypertext Transfer Protocol (HTTP/1.1): Message Syntax and Routing (HTTP/1.1)
# compatibility.with.http.1.0.persistent.connections

Browser compatibility

BCD tables only load in the browser

See also