# Retry-After header > Tells the client how long to wait before making a follow-up request. Source: https://apiguide.dev/headers/retry-after Direction: response Registered: yes Defined in: RFC 9110, Section 10.2.3 Updated: 2026-10-14 ## What is the Retry-After header? The `Retry-After` response header tells the client how long they should wait before retrying the request. ## API Usage & Best Practices * **Send it on 429 and 503**: The specs make it optional (RFC 6585 says a 429 MAY include it, RFC 9110 says a server MAY send it with a 503), but send it anyway whenever you know when capacity returns. Without it, a client can only guess at a backoff. RFC 9110 also defines it on 3xx responses, as the minimum wait before following the redirect. * **Value representation**: Can be expressed either as a decimal integer of seconds to wait (e.g. `Retry-After: 120`) or as an HTTP-date. Seconds are generally preferred in APIs. ## Examples ```http HTTP/1.1 429 Too Many Requests Retry-After: 60 ```