Do you use ETags for performance?

Question

I'm in the process of improving the performance of my app. Some stuff can be browser-cached, some stuff can be public-cached, but the data doesn't change much, and when it does I want the user to get the latest. At some point I'll probably have to setup programmatic cache-busting with a CDN.People don't talk about ETags nearly as much, and I know it's not the same performance gain as a cache, but are people using them in the wild? My instinct is the performance gain from not downloading vs calculating the hash should be a clear win (if a small one).

LinuxBender · Accepted Answer

are people using them in the wild?They are enabled by default in most web server daemons and are widely used [1]. ETags can negatively affect performance under certain conditions and some choose to disable it and instead use their CMS to do other cache busting techniques in combination with cache-control headers that seem to evolve with time the combination of techniques that is. There are probably better and more detailed statistics out there than what I found or at least there better be with the number of bots I see hourly.[1] - https://w3techs.com/technologies/details/ce-etag

gofreddygo · Answer

I use etags mostly for allowing concurrent updates and a way for clients to check for updates without pulling the whole entity.Caching has a much broader scope for performance gains.