Keep-Alive

O cabeçalho Keep-Alive permite que o remetente indique como a conexão deve ser usada, para definir um tempo limite e um máximo de requisições.

O Connection cabeçalho precisa ser definido como "keep-alive" para isso funcionar , Connection e Keep-Alive são ignorados em conexões HTTP/2; Gerenciamento de conexões são feitos por outros mecânismos.

Tipo de cabeçalho General header
Forbidden header name sim

Sintaxe

Keep-Alive: parametros

Diretivas

parâmetros
Uma vírgula separa a lista de parâmetros, Cada consiste de um identificador e um valor separado pelo sinal de igualdade ('='). São possíveis os seguintes identificadores:
  • timeout: indicando a quantidade mínima de tempo que uma conexão deve ser mantida aberta (em segundos). Observe que os tempos limite maiores que o tempo limite do TCP podem ser ignorados se nenhuma mensagem TCP keep-alive estiver definida na camada de transporte.
  • max: indicando o número máximo de pedidos que podem ser enviados nesta conexão antes de fechá-lo. Menor que 0, este valor será ignorado por conexões non-pipelined, pois outra requisição será enviada na próxima resposta. Um HTTP pipeline pode usar isso para limitar o pipelining. 

Exemplos

Uma resposta content o cabeçalho Keep-Alive:

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)

Especificações

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

Compatibilidade dos navegadores

Update compatibility data on GitHub
DesktopMobile
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidFirefox for AndroidOpera for AndroidSafari on iOSSamsung Internet
Keep-AliveChrome 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 YesFirefox Android Full support YesOpera Android Full support YesSafari iOS Full support YesSamsung Internet Android Full support Yes

Legend

Full support  
Full support

Veja também

Última modificação:

, by MDN contributors
Tópicos relacionados
  1. HTTP
  2. Guides:
  3. Resources and URIs
    1. Identifying resources on the Web
    2. Data URIs
    3. Introduction to MIME Types
    4. Complete list of MIME Types
    5. Choosing between www and non-www URLs
  4. HTTP guide
    1. Basics of HTTP
    2. Overview of HTTP
    3. Evolution of HTTP
    4. HTTP Messages
    5. A typical HTTP session
    6. Connection management in HTTP/1.x
    7. Protocol upgrade mechanism
  5. HTTP security
    1. Content Security Policy (CSP)
    2. HTTP Public Key Pinning (HPKP)
    3. HTTP Strict Transport Security (HSTS)
    4. Cookie security
    5. X-Content-Type-Options
    6. X-Frame-Options
    7. X-XSS-Protection
    8. Mozilla web security guidelines
    9. Mozilla Observatory
  6. HTTP access control (CORS)
  7. HTTP authentication
  8. HTTP caching
  9. HTTP compression
  10. HTTP conditional requests
  11. HTTP content negotiation
  12. HTTP cookies
  13. HTTP range requests
  14. HTTP redirects
  15. HTTP specifications
  16. Feature policy
  17. References:
  18. HTTP headers
    1. Accept [Traduzir]
    2. Accept-Charset [Traduzir]
    3. Accept-Encoding [Traduzir]
    4. Accept-Language
    5. Accept-Patch [Traduzir]
    6. Accept-Ranges [Traduzir]
    7. Access-Control-Allow-Credentials [Traduzir]
    8. Access-Control-Allow-Headers [Traduzir]
    9. Access-Control-Allow-Methods [Traduzir]
    10. Access-Control-Allow-Origin
    11. Access-Control-Expose-Headers [Traduzir]
    12. Access-Control-Max-Age [Traduzir]
    13. Access-Control-Request-Headers
    14. Access-Control-Request-Method [Traduzir]
    15. Age
    16. Allow [Traduzir]
    17. Alt-Svc [Traduzir]
    18. Authorization [Traduzir]
    19. Cache-Control
    20. Clear-Site-Data [Traduzir]
    21. Conexão
    22. Content-Disposition [Traduzir]
    23. Content-Encoding [Traduzir]
    24. Content-Language
    25. Content-Length
    26. Content-Location [Traduzir]
    27. Content-Range [Traduzir]
    28. Content-Security-Policy [Traduzir]
    29. Content-Security-Policy-Report-Only [Traduzir]
    30. Content-Type
    31. Cookie [Traduzir]
    32. Cookie2 [Traduzir]
    33. Cross-Origin-Resource-Policy [Traduzir]
    34. DNT [Traduzir]
    35. Date [Traduzir]
    36. Digest [Traduzir]
    37. ETag [Traduzir]
    38. Early-Data [Traduzir]
    39. Expect [Traduzir]
    40. Expect-CT [Traduzir]
    41. Expires
    42. Feature-Policy [Traduzir]
    43. Forwarded [Traduzir]
    44. From [Traduzir]
    45. Host
    46. If-Match [Traduzir]
    47. If-Modified-Since
    48. If-None-Match [Traduzir]
    49. If-Range [Traduzir]
    50. If-Unmodified-Since
    51. Index [Traduzir]
    52. Keep-Alive
    53. Large-Allocation [Traduzir]
    54. Last-Modified
    55. Link [Traduzir]
    56. Location [Traduzir]
    57. Origin [Traduzir]
    58. Pragma [Traduzir]
    59. Proxy-Authenticate [Traduzir]
    60. Proxy-Authorization [Traduzir]
    61. Public-Key-Pins [Traduzir]
    62. Public-Key-Pins-Report-Only [Traduzir]
    63. Range [Traduzir]
    64. Referer [Traduzir]
    65. Referrer-Policy [Traduzir]
    66. Retry-After
    67. Save-Data [Traduzir]
    68. Sec-WebSocket-Accept [Traduzir]
    69. Server
    70. Server-Timing [Traduzir]
    71. Set-Cookie
    72. Set-Cookie2 [Traduzir]
    73. SourceMap
    74. Strict-Transport-Security
    75. TE [Traduzir]
    76. Timing-Allow-Origin [Traduzir]
    77. Tk [Traduzir]
    78. Trailer [Traduzir]
    79. Transfer-Encoding [Traduzir]
    80. Upgrade-Insecure-Requests
    81. User-Agent
    82. Vary [Traduzir]
    83. Via [Traduzir]
    84. WWW-Authenticate
    85. Want-Digest [Traduzir]
    86. Warning [Traduzir]
    87. X-Content-Type-Options
    88. X-DNS-Prefetch-Control
    89. X-Forwarded-For [Traduzir]
    90. X-Forwarded-Host [Traduzir]
    91. X-Forwarded-Proto [Traduzir]
    92. X-Frame-Options [Traduzir]
    93. X-XSS-Protection [Traduzir]
  19. HTTP request methods
    1. CONNECT
    2. DELETE
    3. GET
    4. HEAD
    5. OPTIONS
    6. PATCH
    7. POST
    8. PUT
    9. TRACE
  20. HTTP response status codes
    1. 100 Continue
    2. 101 Switching Protocols
    3. 103 Early Hints [Traduzir]
    4. 200 OK
    5. 201 Created
    6. 202 Accepted
    7. 203 Non-Authoritative Information
    8. 204 No Content
    9. 205 Reset Content
    10. 206 Partial Content [Traduzir]
    11. 300 Multiple Choices [Traduzir]
    12. 301 Moved Permanently [Traduzir]
    13. 302 Found
    14. 303 See Other
    15. 304 Not Modified
    16. 307 Redirecionamento temporário
    17. 308 Permanent Redirect [Traduzir]
    18. 400 Bad Request
    19. 401 Unauthorized
    20. 402 Payment Required [Traduzir]
    21. 403 Forbidden
    22. 404 Not Found
    23. 405 Method Not Allowed
    24. 406 Not Acceptable [Traduzir]
    25. 407 Proxy Authentication Required
    26. 408 Request Timeout
    27. 409 Conflict
    28. 410 Gone
    29. 411 Length Required
    30. 412 Precondition Failed [Traduzir]
    31. 413 Payload Too Large
    32. 414 URI Too Long
    33. 415 Unsupported Media Type
    34. 416 Range Not Satisfiable [Traduzir]
    35. 417 Expectation Failed
    36. 418 I'm a teapot
    37. 422 Unprocessable Entity
    38. 425 Too Early
    39. 426 Upgrade Required
    40. 428 Precondition Required
    41. 429 Too Many Requests
    42. 431 Request Header Fields Too Large [Traduzir]
    43. 451 Unavailable For Legal Reasons
    44. 500 Internal Server Error
    45. 501 Not Implemented
    46. 502 Bad Gateway
    47. 503 Service Unavailable
    48. 504 Gateway Timeout
    49. 505 HTTP Version Not Supported
    50. 511 Network Authentication Required [Traduzir]
  21. CSP directives
    1. CSP: base-uri [Traduzir]
    2. CSP: block-all-mixed-content [Traduzir]
    3. CSP: child-src [Traduzir]
    4. CSP: connect-src [Traduzir]
    5. CSP: default-src [Traduzir]
    6. CSP: font-src [Traduzir]
    7. CSP: form-action [Traduzir]
    8. CSP: frame-ancestors [Traduzir]
    9. CSP: frame-src [Traduzir]
    10. CSP: img-src [Traduzir]
    11. CSP: manifest-src [Traduzir]
    12. CSP: media-src [Traduzir]
    13. CSP: navigate-to [Traduzir]
    14. CSP: object-src [Traduzir]
    15. CSP: plugin-types [Traduzir]
    16. CSP: prefetch-src [Traduzir]
    17. CSP: referrer [Traduzir]
    18. CSP: report-to [Traduzir]
    19. CSP: report-uri [Traduzir]
    20. CSP: require-sri-for [Traduzir]
    21. CSP: sandbox [Traduzir]
    22. CSP: script-src [Traduzir]
    23. CSP: script-src-attr [Traduzir]
    24. CSP: script-src-elem [Traduzir]
    25. CSP: style-src [Traduzir]
    26. CSP: style-src-attr [Traduzir]
    27. CSP: style-src-elem [Traduzir]
    28. CSP: trusted-types [Traduzir]
    29. CSP: upgrade-insecure-requests [Traduzir]
    30. CSP: worker-src [Traduzir]
  22. CORS errors
    1. Reason: CORS disabled [Traduzir]
    2. Reason: CORS header 'Access-Control-Allow-Origin' does not match 'xyz' [Traduzir]
    3. Reason: CORS header 'Access-Control-Allow-Origin' missing
    4. Reason: CORS header ‘Origin’ cannot be added [Traduzir]
    5. Reason: CORS preflight channel did not succeed [Traduzir]
    6. Razão: A requisição CORS não foi bem sucedida
    7. Reason: CORS request external redirect not allowed [Traduzir]
    8. Reason: CORS request not HTTP
    9. Reason: Credential is not supported if the CORS header ‘Access-Control-Allow-Origin’ is ‘*’ [Traduzir]
    10. Reason: Did not find method in CORS header ‘Access-Control-Allow-Methods’ [Traduzir]
    11. Reason: Multiple CORS header 'Access-Control-Allow-Origin' not allowed [Traduzir]
    12. Reason: expected ‘true’ in CORS header ‘Access-Control-Allow-Credentials’ [Traduzir]
    13. Reason: invalid token ‘xyz’ in CORS header ‘Access-Control-Allow-Headers’ [Traduzir]
    14. Reason: invalid token ‘xyz’ in CORS header ‘Access-Control-Allow-Methods’ [Traduzir]
    15. Reason: missing token ‘xyz’ in CORS header ‘Access-Control-Allow-Headers’ from CORS preflight channel [Traduzir]
  23. Feature-Policy directives
    1. Feature-Policy: accelerometer [Traduzir]
    2. Feature-Policy: ambient-light-sensor [Traduzir]
    3. Feature-Policy: autoplay [Traduzir]
    4. Feature-Policy: camera [Traduzir]
    5. Feature-Policy: display-capture [Traduzir]
    6. Feature-Policy: document-domain [Traduzir]
    7. Feature-Policy: encrypted-media [Traduzir]
    8. Feature-Policy: fullscreen [Traduzir]
    9. Feature-Policy: geolocation [Traduzir]
    10. Feature-Policy: gyroscope [Traduzir]
    11. Feature-Policy: layout-animations [Traduzir]
    12. Feature-Policy: legacy-image-formats [Traduzir]
    13. Feature-Policy: magnetometer [Traduzir]
    14. Feature-Policy: microphone [Traduzir]
    15. Feature-Policy: midi [Traduzir]
    16. Feature-Policy: oversized-images [Traduzir]
    17. Feature-Policy: payment [Traduzir]
    18. Feature-Policy: picture-in-picture [Traduzir]
    19. Feature-Policy: speaker [Traduzir]
    20. Feature-Policy: sync-xhr [Traduzir]
    21. Feature-Policy: unoptimized-images [Traduzir]
    22. Feature-Policy: unsized-media [Traduzir]
    23. Feature-Policy: usb [Traduzir]
    24. Feature-Policy: vibrate [Traduzir]
    25. Feature-Policy: vr [Traduzir]
    26. Feature-Policy: wake-lock [Traduzir]
    27. Feature-Policy: webauthn [Traduzir]
    28. Feature-Policy: xr [Traduzir]