Overview#Retry-After is a HTTP Response Header that indicates how long the User-agent SHOULD wait before making a follow-up request.
There are three main cases this header is used:
- When sent with a HTTP 503 (Service Unavailable) response, this indicates how long the service is expected to be unavailable.
- When sent with a HTTP 429 (Too Many Requests) response, this indicates how long to wait before making a new request.
- When sent with a URL redirection response, such as HTTP 301 (Moved Permanently), this indicates the minimum time that the User-agent is asked to wait before issuing the redirected request.