HTTP Header

Retry-After

Response

Tells the client how long to wait before making a follow-up request.

HTTP header reference, syntax, examples, and developer usage.

What is the Retry-After header?

The Retry-After HTTP header is used to transmit metadata between a client and server as part of HTTP requests or responses.

HTTP headers define how content should be interpreted, cached, authenticated, secured, or processed by browsers and APIs.

Direction

This is a response header sent by the server to the client.

Syntax

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

Example

Retry-After: 120

Common use cases

Rate limiting — telling clients when they can retry after a 429
Scheduled maintenance — used with 503 to indicate downtime duration
Delaying follow-up requests after redirects or temporary responses
Advising clients when to retry an API request

Common mistakes

Using the header in the wrong request or response context
Sending invalid header values
Incorrect header syntax
Assuming the header automatically changes server behaviour

Practical developer insight

Retry-After accepts either a number of seconds or an absolute HTTP date. Most commonly seen with 429 Too Many Requests and 503 Service Unavailable. Well-behaved API clients should respect it to avoid unnecessary load — but note that some browsers and HTTP clients ignore it entirely, so it should not be the only retry control mechanism.