To ETag or not to ETag

[pmeenan]

(thread migrated from sourceforge forum - originally posted 6/25/2008)

This one's been bothering me for a while.

ETags exist for a reason. It's part of the standard HTTP protocol ( http://www.w3.org/Protocols/rfc2616/rfc2...l#sec14.19 ) and is designed to help optimize cache utilization.

Cacheing is generally good, so why is ETag bad?

It can only mean that either:

1) the spec is broken
2) its implementation is broken

Now, I have seem some discussion that says it's easy to break (server-side), so the same resource may have different ETag values which could lead to a cache miss, but what if you're a web guy who knows what he's doing and has consistent ETags?

Why should my sites get penalized for using correctly-implemented W3C standards?