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

Syntax

http

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

undefined

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.