nginx caching headers

Maxim Dounin mdounin at
Thu Jul 3 09:45:18 UTC 2014


On Wed, Jul 02, 2014 at 11:26:54PM -0400, eiji-gravion wrote:

> Are there any specific reasons why nginx has both ETags and the Last
> Modified headers being sent? From my understanding, this is a bit redundant
> for most situations.

This is required to support both clients using Last-Modified as a 
cache validator, and ETag as a cache validator.  As nginx doesn't 
know what a client will use, it returns both.  (And this is 
identical to what other servers out there do.)

Originally ETag support was added to support download resumption 
in IE9, it needs strong entity tags to be able to resume 
downloads using range requests.  And obviously there are lots of 
clients which don't support ETag.

Maxim Dounin

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