''<p>werw51bipsvj [[#question-1384220|said]]</p>'' <blockquote>When trying to clear cookies and site data on first opening Firefox 103.0, on a iMac 10.15.7 I typically have 363 KB of Cashed Web Content even after browsing in Privacy mode and shutting Firefox down. When attempting to erase this data it always leaves 264 KB until I take other measures to get rid of the data. Why is this?</blockquote> You can see what is stuck in the cache by typing or pasting '''about:cache''' in the address bar and then pressing Return to load the page. There's a link in the disk cache section to view the file list. Usually the issue is that Firefox has retrieved content for its own purposes, such as the new tab page. You shouldn't find any sites you visited in private windows listed here. <blockquote>Second when opening Firefox I get a mozilla.cloudflare-dns.com notice which I deny access to. What is the purpose of this connection?</blockquote> Firefox uses Cloudflare for "DNS over HTTPS" so my guess is that you are using that feature. If you want to disable it and test again, check out the steps in the following article: [[Firefox DNS-over-HTTPS]]. <blockquote>Third I also get mozilla.cloudflare-dns.com plugin-container attempt which I also block. What is the purpose of this connection?</blockquote> plugin-container might be used for Widevine (used to play DRM video on Netflix, Amazon, etc.) and any other plugins running in your Firefox (there are not many any more). Not sure whether that is really needed or it's just looking up the address to check for updates.