4 “About:Config” Tricks to Extend the Functionality of Firefox

Firefox is, by nature, a relatively unusual web browser. While in its default guise, it is satisfactory for most users, and there exists a subset that desires to do more than the immediately obvious. This results in downloadable extensions purporting to fill in gaps in the browser’s features.

There is also the oft-forgotten “about:config” page within the browser. Many users forget it exists, though the configuration page is one of the most powerful within the browser if you know exactly what you seek. Here are some about:config tricks you can use to improve your Firefox browser.

To access the “about:config” page, all you have to do is to open a new tab in Firefox and type about:config in the address bar. This will open up a warning page.

Accept the warning prompt.

Click the button “I’ll be careful, I promise!” and you are now in the “about:config” page.

Closing a browser session normally means losing the tabs you had open. Combing through the history might work if you need to find something again but not always. One tweak is all it takes to save your session.

In the text box along the top of the “about:config” page, type showQuitwarning to bring up the string “browser.showQuitwarning”. This should be appearing as “false” for now.

Bring up the string 'browser.showQuitwarning.'

Double click the string of text; this will cause it to turn bold and “false” becomes “true”.

Click 'Save and Quit.'

Attempt to close Firefox and a new prompt window will appear asking if you wish to save your tabs for the next browsing session. Give it a whirl and see what you think – the setting can be changed at will.

Note that the save prompt takes precedence over the usual message about closing with numerous tabs open. If both are set to appear, then only this message will appear. The browser will also save only one session, so bringing back an older session means going through your history.

A new tab in Firefox.

If you have used Opera or tried Vivaldi, you may have felt a subtle but distinct difference. When you close all the tabs open in Firefox, the browser closes. This is not the case for the aforementioned browsers. With this tweak, Firefox behaves in the same way.

In the “about:config” page, type CloseWindowWithLastTab.

Type 'CloseWindowWithLastTab.'

This is another Boolean string, meaning it can only be “true” or “false.” Its default state is “true,” meaning that when the last tab closes, so does the browser. Double click the string to change it to “false.”

To test the effect, close all your tabs. Upon closing the final tab, it should refresh to your homepage rather than actually closing the browser.

Show the full URL in your address bar.

Ever shared a link with friends and found they can’t open it? Chances are it’s something to do with the “http://” prefix to the URL being malformed or not included at all. By default, Firefox doesn’t even show this prefix – but it can, and control over this behaviour exists in the about:config settings.

Display the URL prefix.

Open about:config and click the search box. Type trimURL and there will be only one string, “browser.urlbar.trimURLs.”

Observe the string’s current state. If this has not been modified, it will be ‘true.’ Double click the string and its text will become bold but more importantly the value will now be ‘false.’

Secure website verification.

Check out the address bar and the prefix should appear. Issues with sharing links are uncommon, but this tweak should only simplify things further. It also has the benefit of making clear whether you’re on a secured connection with an https:// prefix or not, although Firefox does have its own indicator by the address bar.

Changing between programs in Windows can be done using the taskbar or the Alt+Tab key combination, and it is possible you’ve used both at different times. Firefox, somewhat surprisingly, has a similar feature buried deep within its about:config window, but it can be introduced with a single change.

Add previews similar to Windows' Alt+Tab.

Begin, as usual, by opening the about:config page and accepting the warning associated with it.

Enter the search bar along the top of the window and type ctrltabs.previews. This will bring up one result: a Boolean string which is, by default, ‘false.’ Double click it and change the status to ‘true.’

Tab preview via Ctrol+Tab in Firefox.

No visible change is made to the browser, and there is no need to restart it for anything to take effect. The real change happens when the key combination of “Ctrl + Tab” is held. Rather than popping open the Bookmarks sidebar, it will create an interface for changing tabs quickly.

Changing the tab can be done either by moving the mouse cursor to your selection or by pressing the Tab key repeatedly.

Depending on how many tabs you have open at a time, this could be a massive boon. Used in conjunction with the saved session option, it could totally change your browsing habits.

If you’ve used the about:config page in Firefox before this article or as a result of it, it may have occurred to you that it is a back-end version of the settings window. In many ways it is, but as this article clearly demonstrates it is also substantially more.

As ever, exercise caution when changing settings in this manner; while the examples listed will not compromise the browser’s functionality, others potentially could.