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HTTP Header
Expires
CachingSpecifies a date/time after which the response is considered stale.
HTTP header reference, syntax, examples, and developer usage.
What is the Expires header?
The Expires 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 header may appear in both HTTP requests and responses.
Syntax
Expires: <http-date>
Example
Expires: Thu, 01 Dec 2026 16:00:00 GMT
Common use cases
- Cache expiration control
- Legacy caching behavior
- Static asset delivery
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