Firefox doesn't get enough love these days, but it's still the most customizable browser around thanks the numerous options in about:config . Here are 10 under-the-hood Firefox tweaks you should try out.



If you aren't familiar with about:config , it's simple: just type about:config into Firefox's address bar and you'll be greeted with hundreds of hidden settings tweaks that change how Firefox works. In some cases, these are quirky or unfinished features, but in other cases, they just change certain parameters that Firefox uses by default. Double-click on any item to change it, but be careful—some options may act weird, slow down Firefox, or break it altogether. Check out Mozilla's Knowledge Base entry for more information.

We've shared a number of about:config tips over the years, but it's been awhile, so we thought we'd revisit some of our favorites—along with some new ones we haven't seen before.

Disable the Delay When Installing New Extensions


When you install a new extension, Firefox makes you wait 5 seconds before installing to ensure you pay attention to where it's coming from. It ends up just being an annoyance. To turn the delay off, just open up about:config and search for:

security.dialog_enable_delay

...and set the value to 0 .

Give Bookmarks Higher (or Lower) Weight in the Awesomebar Suggestions

When you type something into the Awesomebar, Firefox ranks its suggestions by something it calls "Frecency," a combination of how frequently and recently you visited a given URL. However, you can adjust the "weight" it gives to certain types of URLs—like bookmarks—with a few about:config tweaks.


You can do a lot with this, and we won't go through all of it here, but let's say for example that you wanted to give bookmarks a higher weight (so Firefox is more likely to suggest them near the top of the list) or no weight (so you don't see bookmarks at all in the Awesomebar suggestions). Just open about:config and search for:

places.frecency.unvisitedBookmarkBonus

The default value is 140 , so if you want bookmarks to rank higher. increase this number. If you want them to rank lower, decrease this number, or set it to 0 to eliminate bookmark suggestions entirely. For more information, check out Mozilla's developer page and Knowledge Base article on frecency settings.


Increase the Number of Suggestions in the Awesomebar Dropdown


By default, when you type something into Firefox's Awesomebar, it spits out 12 suggestions for you. If you'd like more, just head into about:config and search for:

browser.urlbar.maxRichResults

Change the value to however many suggestions you want. Alternatively, set it to -1 if you'd like to disable the suggestions altogether.


Open Search Results in a New Tab


By default, Firefox has a search box in the upper-right hand corner from which you can Google things with ease. When you type in a search term, it opens the results in your current tab, which is annoying if you want to keep your current tab open.

To change this behavior, open about:config and search for:

browser.search.openintab

Double-click the setting to change it to True , after which your search results should open in a new tab.


If you use Firefox's Awesomebar to search instead of the search box, you can get the same effect by pressing Alt+Enter when you search.


Tweak the Way Firefox Shows URLs in the Address Bar


These days, Firefox displays URLs a bit differently so they're easier to read. By default, it eliminates the "http" before a URL, and greys out text beyond the main domain of a site (such as "lifehacker.com").

To turn off the URL greying, open about:config and search for:

browser.urlbar.formatting.enabled

Double-click it to change it to False , and you should find the URLs display in all black text.


To unhide the "http" portion of a URL, search for:

browser.urlbar.trimURLs

Double-click the setting to change it to False .

Disable Compatibility Checking for Extensions


Isn't it annoying when a developer hasn't updated their extension to "work" with a new version of Firefox, even though it actually works fine? You can disable these checks. Open about:config and right-click on an empty space. Choose New > Boolean and create a new setting called:

extensions.checkCompatibility

Set its value False . Alternatively, you can install the Add-On Compatibility Reporter extension to achieve the same effect.


Make Firefox's Spell Checker More Useful


Firefox's spell checker is fine, but there are two useful options in about:config that make it more helpful. First, you may have noticed that Firefox only enables its spell checker in multi-line text boxes, not single-line text boxes like many search boxes. To enable it in all text boxes, search for:

layout.spellcheckDefault

...and its value to 2 . You should then see those familiar squiggly red lines in search boxes and other single-line forms.


Speaking of those squiggly red lines, do you ever wish they were a bit more obvious or harder to ignore? A hidden setting makes it so: open up about:config and right-click on an empty space. Choose New > Integer, and name it:

ui.SpellCheckerUnderlineStyle

Set its value to 0 for no highlighting, 1 for a dotted line, 2 for long dots, 3 for a single straight line, 4 for a double underline (my personal favorite, shown above), and 5 for the default squiggly line.


Preview Tabs in the Ctrl+Tab Switcher


You know how you can cycle through your open programs in Windows with Alt+Tab? Well, you can do something similar with Firefox's open tabs with Ctrl+Tab. By default, it just moves you to the next tab, but with an about:config tweak, you can have it show you previews like Windows' task switcher does. To do so, just search for:

browser.ctrlTab.previews

Set its value to True and you're on your way.

Add More Rows and Columns to Firefox's New Tab Page


By default, Firefox's new tab page shows 9 sites. If you want it to show more, you can do so! Just head to about:config and search for:

browser.newtabpage.rows

and

browser.newtabpage.columns

Set each to the number you want, and you'll be able to fit more sites on that new tab page.


Disable Animations for New Tabs, Tab Groups, and Full Screen


Animations are cool, but they can also slow things down if you're on a particularly old machine. To turn off the animations for new tabs, Firefox's "Tab Groups" feature, and the transition to full screen, just search for the following options (respectively):

browser.tabs.animate<br>browser.panorama.animate_zoom<br>browser.fullscreen.animateUp


Set the first two of these to False and/or the last to 0 to turn them off.

These are just a smattering of the options you'll find in about:config , but they're some of our favorites. To see more, check out Mozilla's huge list, or go exploring for yourself. Be sure to check out our power user's guide to Firefox and our Lifehacker Pack for Firefox for even more great tweaks and power-ups.


Title image remixed from Nemo and A Aleksii (Shutterstock) .