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Connection header - HTTP | MDN
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Connection header

Baseline Widely available

This feature is well established and works across many devices and browser versions. Its been available across browsers since July 2015.

The HTTP Connection header controls whether 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 subsequent requests to the same server on the same connection.

Warning: Connection-specific header fields such as Connection and Keep-Alive are prohibited in HTTP/2 and HTTP/3. Chrome and Firefox ignore them in HTTP/2 responses, but Safari conforms to the HTTP/2 spec requirements and does not load any response that contains them.

All hop-by-hop headers, including the standard hop-by-hop headers (Keep-Alive, Transfer-Encoding, TE, Connection, Trailer, Upgrade, Proxy-Authorization, and Proxy-Authenticate) must be listed in the Connection header, so that the first proxy knows it has to consume them and not forward them further.

The default value of Connection changed between HTTP/1.0 and HTTP/1.1. Therefore, to ensure backwards compatibility, browsers often send Connection: keep-alive explicitly, even though it's the default in HTTP/1.1.

Header type Request header, Response header
Forbidden request header Yes

In this article

Syntax

http
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. Keeping a connection open 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.

Specifications

Specification
HTTP Semantics
# field.connection

Browser compatibility

See also

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  1. HTTP
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  3. Overview of HTTP
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  13. Conditional requests
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  15. Client hints
  16. User-Agent reduction
  17. Compression Dictionary Transport
  18. Network Error Logging
  19. Content negotiation
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  20. Browser detection using the UA string
  21. Connection management in HTTP/1.x
  22. Protocol upgrade mechanism
  23. Proxy servers and tunneling
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  24. Security and privacy
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    7. Cross-Origin Resource Sharing (CORS)
    8. CORS errors
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      2. Reason: CORS header 'Access-Control-Allow-Origin' does not match 'xyz'
      3. Reason: CORS header 'Access-Control-Allow-Origin' missing
      4. Reason: CORS header 'Origin' cannot be added
      5. Reason: CORS preflight channel did not succeed
      6. Reason: CORS request did not succeed
      7. Reason: CORS request external redirect not allowed
      8. Reason: CORS request not HTTP
      9. Reason: Credential is not supported if the CORS header 'Access-Control-Allow-Origin' is '*'
      10. Reason: Did not find method in CORS header 'Access-Control-Allow-Methods'
      11. Reason: expected 'true' in CORS header 'Access-Control-Allow-Credentials'
      12. Reason: invalid token 'xyz' in CORS header 'Access-Control-Allow-Headers'
      13. Reason: invalid token 'xyz' in CORS header 'Access-Control-Allow-Methods'
      14. Reason: missing token 'xyz' in CORS header 'Access-Control-Allow-Headers' from CORS preflight channel
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  25. Reference
  26. HTTP headers
    1. Accept
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  27. HTTP request methods
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    8. PUT
    9. TRACE
  28. HTTP response status codes
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    4. 103 Early Hints
    5. 200 OK
    6. 201 Created
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    60. 510 Not Extended
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  29. CSP directives
    1. base-uri
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    3. child-src
    4. connect-src
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    6. fenced-frame-src
    7. font-src
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    19. sandbox
    20. script-src
    21. script-src-attr
    22. script-src-elem
    23. style-src
    24. style-src-attr
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    26. trusted-types
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    28. worker-src
  30. Permissions-Policy directives
    1. accelerometer
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    3. aria-notify
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    30. magnetometer
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    41. screen-wake-lock
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    45. summarizer
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  31. HTTP resources and specifications
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