How do you create eTags?

I often use Pingdom to check on a websites page to check it's download score but don't get hung up to much about the results as often many are out of your hands if using Xara to create a site. One thing that does niggle me is the 'Configure eTags' warning.

I've done numerous searches on how I can create eTags but never found one single method of doing so. No big sweat, just out of interest.

Anyone any idea re this?

Of course, I don't.

That is nothing you can influence in Xara or by scripting. It is a server setting. For example the apache documentation:
https://httpd.apache.org/docs/2.2/mo....html#fileetag
It is used to help the browser to decide if a file was read before and can safely be taken from the cache.

Thanks for the link Siran. I think I'll avoid eTags because that's way beyond my comprehension.

Furthermore I believe this is a good reason to avoid them:

Quote:

---

Because we’re now using Cache-Control and Expires, there is no need for these other two [last_modified & etag], except for HTML documents, where one of them should be left on.


Another reason to use Cache-Control and Expires instead of ETags and Last Modified is because more and more hosting companies are using cluster (cloud) servers. ETags and Last Modified only work if the file that is being tagged comes from the exact same server. If your host is using a cluster of servers, the ETags and Last Modified will not work, but Cache-Control and Expires will.

---

Source

Both would have their advantages. If a checksum (MD5, SHA1,...) of the file was used it would be much more reliable than Expires. On the other hand the HTTP header has to be read each time the file is required to check the ETag.
Short Expires in combination with a reliable ETag might be very efficient, but that is not up to us... :(

Thanks again ;)