ETag header -- what is it?

[Finder]

The server header checker shows that apache is creating an etag and sending out this value, but what is it? I did some surfing and found some vague references to caching, but nothing informative.

[jdMorgan]

Finder,

It's an Entity Tag - a "freshness" indicator if you will, used for cache management. More information is available in the Apache Core Features [httpd.apache.org] documentation, under FileETag [httpd.apache.org].

Jim

[Finder]

Thanks for the link! Interesting... does anyone bother configuring this for caching efficiency or do people mainly leave the default values alone?

[jdMorgan]

I just use the default E-Tag setting (All). I also have the server set up to provide correct cache-control and last-modified HTTP headers using mod_expires.

Jim