Retry-After header

The HTTP Retry-After response header indicates how long the user agent should wait before making a follow-up request. There are three main cases this header is used:

In a 503 Service Unavailable response, this indicates how long the service is expected to be unavailable.
In a 429 Too Many Requests response, this indicates how long to wait before making a new request.
In a redirect response, such as 301 Moved Permanently, this indicates the minimum time that the user agent is asked to wait before issuing the redirected request.

Header type	[Response header](https://developer.mozilla.org/en-US/docs/Glossary/Response%20header)

Syntax

Retry-After: <http-date>
Retry-After: <delay-seconds>

Directives

<http-date>
- : A date after which to retry. See the Date header for more details on the HTTP date format.
<delay-seconds>
- : A non-negative decimal integer indicating the seconds to delay after the response is received.

Examples

Dealing with scheduled downtime

Support for the Retry-After header on both clients and servers is still inconsistent. However, some crawlers and spiders, like the Googlebot, honor the Retry-After header. It is useful to send it along with a 503 response, so that search engines will keep indexing your site when the downtime is over.

Retry-After: Wed, 21 Oct 2015 07:28:00 GMT
Retry-After: 120

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