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An obscured, but powerful, method of configuring Firefox. You can edit settings by entering about:config in the address bar. From there you can search for settings and edit them.


In the 'New Bookmark' and 'Edit This Bookmark' menus that appear when you click the bookmark icon, there's a list of the most recently used folders in the 'Folder' drop-down. You can increase this by searching for browser.bookmarks.editDialog.maxRecentFolders, and increasing or decreasing the number to suit.

Dark Mode

To tell websites that you prefer to view pages in dark mode (or…)

  1. about:config
  2. Find ui.systemUsesDarkTheme
    • 0 = light
    • 1 = dark
    • 2 - no prefernce

If you want your UI to be dark you need to use a theme.


To disable automatic updates you now have to do it though about:config :/

  1. Enter about:config into the address bar,
  2. Search for 'update'
  3. Find
  4. Double-click on that link to change true to false.


Address Bar

You can narrow your searches by starting them with:

^ History
* Bookmarks
% Tabs
# Page titles
@ URLs
+ Tags, separate with spaces for multiple

They're easy to forget, but there's a little add-on you can use to remind yourself: location-bar-characters.

Reader View

Reader View is a nice clean way to read stuff online. Makes a lot of news and writing sites actually tolerable. Strips out everything but the text and images. Especially great on mobile, as it will turn pages that aren't designed for a small screen into something comfortable to read in that format.

Some add-ons for enhancing reader view (that I'm yet to test 8-)):


Firefox has dropped support for RSS, it doesn't even render feeds anymore. You can re-add support with plugins, plus add some other useful features:

  • I use feed-preview to get the old RSS functions back. It renders previews of feeds, and puts an icon in the address bar when feeds are present. There are other add-ons that do the same thing.
  • I use youtube-rss-finder to make it easier to get feed links for Youtube. Like Feed Preview, it puts an icon in the address bar.


As an alternative to add-ons like Stylus, you can simply add CSS rules to the file userContent.css. It's slightly annoying in that you have to restart Firefox for it to reload the file, but you can use Stylus or the built-in developer tools (you can load files in the 'style editor' tab) to preview things. For styling Firefox itself you create a file called userChrome.css.


  1. Open about:config and turn toolkit.legacyUserProfileCustomizations.stylesheets to True.
  2. Open your profile directory (for me it's ~/.mozilla/[profile name]) and create a directory called chrome if it doesn't exist.
  3. Inside chrome create a file called userContent.css
  4. Add rules to this, enclosed within @-moz-document domain([url]) {} that references the site you wish to target.
    • Instead of domain([url]) you can use url, regex, etc. See: @document#Syntax.
    • For userChrome.css you don't need the @-moz-document stuff, just add the rules like normal.


Hide useless search results
@-moz-document domain( {
	.result[data-domain=""] {

See Also


Browser works, pages don't load

Sometimes after a crash Firefox will start-up just fine, but pages won't load. Deleting ~/.cache/mozilla seems to fix it.

I ended up making an alias in my .bashrc:

alias fix-firefox='rm -rf ~/.cache/mozilla/firefox'

See Also

firefox.txt · Last modified: 2021/06/28 00:10 by rjt