Etags in apache headers

what are they, what are best settings?

[amznVibe]

I noticed one of my shared hosting server just started showing Etags in the headers
example:

ETag "1e40c7-4f2f-3f78f85d"

I found this documentation to control them (not sure if htaccess can override the httpd.conf in this case)
[httpd.apache.org...]

but I don't completely understand how browsers/proxies use them?

Stuff like this only confuses me further:
[studio.tellme.com...]

Thanks for any help!

[DaveAtIFG]

I don't either! But this from the Apache directive you linked to:

The ETag value is used in cache management to save network bandwidth.

I'm inclined to think that it will be up to each browser/proxy to decide if or how to use ETags. Perhaps some "conventions" will or have emerged as to their use but I have no idea where to look or how to find them.

From your other link:

An ETag is an HTTP response header returned by an HTTP/1.1 compliant Web server such as Apache 1.3x.

ETags are "new." They first became available with the HTML/1.1 spec.

[amznVibe]

More research shows they are appearing when I use the mod_expires directive.

Apache must auto-integrate the two (or my host has some options doing this).

Etags seem to show the file size and time as an origination stamp, so maybe the proxies/caches can determine when to update if they ignore the expires info?

Oh and apparently I *can* override their display and format in htaccess.