Hi Oleg, Firefox should revalidate cached script files when you use F5/the Reload button/Ctrl+R, but in Firefox 79+, it definitely will not routinely check for updates to cached CSS files before expiration. I agree this is similar to Chrome, based on a test page I built here to compare the two: https://www.jeffersonscher.com/csscache/ So your workaround options include: '''(A) On your server, disable caching of .css files''' Only practical for development servers, not production servers. However, this would bypass the issue for all browsers you need to test in. '''(B) In Firefox, disable caching during development''' * While Dev Tools are open: There is a checkbox for this in the Network Monitor tool. The corresponding preference in about:config is '''devtools.cache.disabled''' (double-click to toggle). * Completely: In about:config, look for '''browser.cache.disk.enable''' and '''browser.cache.memory.enable''' (double-click to toggle). '''(C) When reloading, bypass the cache''' This doesn't require any configuration changes, but there's an extra finger (key) involved each time. Either: * Shift+click the Reload button * Ctrl+F5 * Ctrl+Shift+R (seems a bit less reliable than the other two methods) ---- ''New workaround as of Sept. 22:'' '''(D) Use an extension to disable caching of .css files from relevant servers''' I created an extension that applies '''cache-control: no-store''' to text/css responses from hosts you specify: * https://addons.mozilla.org/firefox/addon/no-cache-no-store-for-css/ * https://github.com/jscher2000/No-Cache-No-Store-Extension (Still trying to figure out a good user interface for managing addition and removal of host permissions. Hopefully Firefox will have a native one at some point.)

I did end up creating an extension: https://addons.mozilla.org/firefox/addon/no-cache-no-store-for-css/ It applies '''cache-control: no-store''' to text/css responses from hosts you specify. That prevents caching, so they are re-retrieved for a plain F5 or Ctrl+r.