The Retry-After HTTP response header tells a client how long to wait before a follow-up request or when it may retry. It lets an API provide more specific timing than a client's normal exponential back-off. section 29.3.3
Format the delay deliberately:
- Use a duration in seconds, such as 120, as the usual choice. section 29.3.3
- A date is also valid, but clock differences between server and client can produce substantially incorrect waits. section 29.3.3
- Apply the header when the service knows when a transient failure is likely to succeed, while retaining retry limits and delay caps. section 29.6
Client honoring a dictated delay
A retrying client checks for Retry-After, converts a value such as 120 seconds to milliseconds, and waits that duration. Without the header, it uses exponential back-off with random jitter.
