HTTP headers
Vary HTTP Header Meaning
Vary tells caches which request headers affect the response.
Meaning
The server is saying cached variants must be keyed by one or more request fields.
Where it appears
Servers send it when content negotiation, compression, language, or personalization affects the response.
What to check
Check that Vary includes only headers that truly change the response; over-broad Vary can damage caching.
Example
Vary: Accept-Encoding, Accept-LanguageReferences
- Registry
- IANA HTTP Field Name Registry
- Guide
- MDN Vary