Definition of ETag header (https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/ETag):
The ETag HTTP response header is an identifier for a specific
After some research, I found a great tutorial on Medium by Alex Barashkov: "Best practices for cache control settings for your website".
Alex writes:
I recommend you apply
Cache-Control: no-cache
to html files. Applying “no-cache” does not mean that there is no cache at all, it simply tells the browser to validate resources on the server before use it from the cache. That’s why we need to use it with Etag, so browsers will send a simple request and load the extra 80 bytes to verify the state of the file.