The "remote-settings" database stores downloaded translation files which can be quite large, you can make it smaller by [[Firefox Translation#w_configure-installed-languages|removing languages]]. Explore the database for yourself with the [https://firefox-source-docs.mozilla.org/devtools-user/browser_toolbox/index.html Browser Toolbox]'s Storage tab.

''<p>zeroknight [[#answer-1650465|said]]</p>'' <blockquote>The "remote-settings" database stores downloaded translation files which can be quite large, you can make it smaller by [[Firefox Translation#w_configure-installed-languages|removing languages]]. Explore the database for yourself with the [https://firefox-source-docs.mozilla.org/devtools-user/browser_toolbox/index.html Browser Toolbox]'s Storage tab. </blockquote> Well that's exactly the issue, and removing the installed languages removed the storage hog. Thank you. Before I mark this as solved, do you have any idea what could have initiated this "all known languages" offline installation? I can't think of anything I would have intentionally done, unless it was agreeing to one of those frequent popups that keep happening, like google's obsession with tracking my location.