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HTTP Header
Vary
CachingIndicates which request headers influence the selected response representation.
HTTP header reference, syntax, examples, and developer usage.
What is the Vary header?
The Vary 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
Vary: Accept-Encoding
Example
Vary: Accept-Encoding, Origin
Common use cases
- Caching correctness
- Compression-aware responses
- CORS-related cache behavior
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