HTTP header Retry-After

Servers send the “Retry-After” header field to indicate how long the user agent ought to wait before making a follow-up request. When sent with a 503 (Service Unavailable) response, Retry-After indicates how long the service is expected to be unavailable to the client. When sent with any 3xx (Redirection) response, Retry-After indicates the minimum time that the user agent is asked to wait before issuing the redirected request.

The Retry-After field value can be either an HTTP-date or a number of seconds to delay after receiving the response.

Retry-After = HTTP-date / delay-seconds

A delay-seconds value is a non-negative decimal integer, representing time in seconds.

delay-seconds = 1*DIGIT

Two examples of its use are

Retry-After: Fri, 31 Dec 1999 23:59:59 GMT Retry-After: 120

In the latter example, the delay is 2 minutes.