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/HTTP

Connection

The Connection general header controls whether or not the network connection stays open after the current transaction finishes. If the value sent is keep-alive, the connection is persistent and not closed, allowing for subsequent requests to the same server to be done.

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.

Except for the standard hop-by-hop headers (Keep-Alive, Transfer-Encoding, TE, Connection, Trailer, Upgrade, Proxy-Authorization and Proxy-Authenticate), any hop-by-hop headers used by the message must be listed in the Connection header, so that the first proxy knows it has to consume them and not forward them further. Standard hop-by-hop headers can be listed too (it is often the case of Keep-Alive, but this is not mandatory).

Syntax

Connection: keep-alive
Connection: close

Directives

close
Indicates that either the client or the server would like to close the connection. This is the default on HTTP/1.0 requests.
any comma-separated list of HTTP headers [Usually keep-alive only]
Indicates that the client would like to keep the connection open. Having a persistent connection is the default on HTTP/1.1 requests. The list of headers are the name of the header to be removed by the first non-transparent proxy or cache in-between: these headers define the connection between the emitter and the first entity, not the destination node.

Browser compatibilityUpdate compatibility data on GitHub

Desktop
Chrome Edge Firefox Internet Explorer Opera Safari
Connection Yes 12 Yes Yes Yes Yes
Mobile
Android webview Chrome for Android Firefox for Android Opera for Android Safari on iOS Samsung Internet
Connection Yes Yes Yes Yes Yes Yes

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https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Connection