Super UserWhat do you think is the most useful about:config setting in Firefox?
[+25] [21] Jeff Leonard
[2009-07-17 04:20:32]
[ firefox hack about-config ]

What about:config settings do you find the most useful in Firefox?

One setting per comment please, so we can vote on them.

(7) This should be community wiki. - phenry
As @Nik Notes below: This may void your warranty ;-) Back up your settings now before you start tinkering. - Jeff Leonard
(3) about:robots , clearly. - glasnt
about:robots isn't an about:config setting - Josh
[+17] [2009-07-17 04:36:46] onEnterFrame


Saves your login info for ntlm so you can easily do single sign off for enterprise sites, like share point, etc.

(3) Superseded by network.negotiate-auth.trusted-uris for Kerberos (Active Directory) networks. network.negotiate-auth.delegation-uris can also be rather useful for intranet apps... See: - Shog9
[+13] [2009-07-17 05:07:00] dbr

layout.spellcheckDefault [1] set to 2 will enable spell checking in regular input boxes, not just <textarea>


Isn't that a right-click option on all input boxes? - grawity
@gravity: Yes, but this saves you a right-click. :) - musicfreak
[+10] [2009-07-17 23:27:31] heavyd = true

I hate having those searches take over my current tab.

And, for linux systems only, but this one really throws me off when I don't have it set:

middlemouse.contentLoadURL = false

(3) +1 for disabling the middle mouse click. So true. - Nikhil Chelliah
What does the middle button do? - Kiewic
(2) If you click the middle button(scroll wheel on most mice) on a tab it will close the tab. On most distributions of linux the default behavior is to load whatever is in clipboard as the URL for the tab you click. - heavyd
[+8] [2009-07-17 23:13:02] ldigas

browser.tabs.closeWindowWithLastTab set to false enables you to close all tabs, including the last one without closing Firefox

[+6] [2009-07-17 22:49:07] CesarB


Set it to false, of course.

Ok? What exactly does this do? - wahle509
[+6] [2009-07-17 04:23:51] nik

A popular one for firefox 3.5 is the Multi-touch tab switch [1].
And, here is a list of popular about:config hacks [2].

You are probably going to start tinkering with your about:config settings now.
Here are a few tip references that might be useful on your way.
Please note that you could break your firefox configuration -- backup and care are advocated.

When you play with the config lines too much and want to undo something you don't want,
follow these steps to remove customized about:config entries [3].

The config area can start looking like your registry with old and unused entries,
if you often add and remove plugins/extensions.
This is when you need to get more serious (and under the hood)
to start cleaning up from the pref.js file directly [4].


[+4] [2009-08-27 15:51:22] DisgruntledGoat

image.animation_mode = none

This will stop animated GIFs from moving. Personally I find them very annoying!

[+4] [2009-07-21 17:33:19] community_owned

I set:

browser.fullscreen.autohide : false

when using a netbook since I want to use fullscreen (hide the system taskbar etc.) but still want to see my tabs without having to move the mouse up (with the tiny touchpad).

It's also useful when opening a new tab with Ctrl-T. In normal view, this will open a new tab and move the focus to the address bar so I can immediately type an address or query. However, the focus change will not happen when in fullscreen with the bars hidden. With the fullscreen autohide disabled, this behaves as it would in normal view.

[+3] [2009-07-20 16:47:35] Eduardo Molteni

Change browser.tabs.loadDivertedInBackground to true and then you can click your links in the mail and feedreader programs without bringing Firefox as the front window.

[+3] [2009-07-17 04:41:51] Nick Dandoulakis

If you want the download completed alert window to show up (or not show up).

about:config = true // or false

[+3] [2009-07-17 09:53:37] grawity


Useful when you encounter "smart" websites.

[+3] [2009-07-17 21:53:19] Michelle

brower.tabs.tabMinWidth = 20

because I open lots of tabs

(2) Try FaviconizeTab if you want really narrow tabs - just teh favicon or you can expand it to normal width. - CAD bloke
Beat me to it CAD! - wahle509
[+2] [2009-07-17 10:04:19] tjrobinson

Every time a major new version comes out:

extensions.checkCompatibility          false

See: mozillaZine [1]


Why the downvote? - tjrobinson
(5) This is kind of a bad idea... There's a reason that flag defaults to true: until add-on authors have a chance to look over their code, test with the new version, and verify that nothing broke, you might well encounter odd or even dangerous side effects by enabling extensions not intended to run with the new version. You're better off enabling them one at a time and testing yourself... or waiting for the author to update them for the new version. - Shog9
Agree with @Shog9, don't know why you'd want to set this as false. - musicfreak
(1) "you might well encounter odd or even dangerous side effects by enabling extensions not intended to run with the new version"... or, it might work perfectly, as with pretty much every extension I've forced to work with new Firefox versions.. - dbr
Fair enough, I still think it's useful to know though as a lot of useful extensions are inactive but work perfectly well on newer versions. - tjrobinson
(1) Going from 3.0 to 3.5 kicked out most of my extensions. Of course, all of them still worked. I'd recommend the nightly tester tools above this, though, just in case sort of thing. - Phoshi
Like @Phoshi I recommend the nightly tester tools from, because it allows one to override the compatibility per add-on. (I actually need it to keep keyconfig running, to solve issues with Cmd-Left on a Mac --…) - Arjan
[+1] [2009-07-17 04:35:19] John T

browser.urlbar.maxRichResults will allow you to change how many suggestions from your history the awesome bar will display.

Changing view_source.editor.external to true will allow you to view source code in your external editor of choice, as you specify in view_source.editor.path.

browser.sessionhistory.max_entries defines how many pages you can traverse through with the back/forward buttons.

(1) One setting per answer, please. - Adam Crume
[+1] [2009-08-27 15:56:43] DisgruntledGoat

browser.sessionhistory.max_total_viewers = 5 (or more)

Specifies how many recent pages Firefox holds in the cache (in memory I assume as opposed to on disk), so when you go back and forward through history, they load near-instantly. Not quite as good as Opera, which does load pages instantaneously but it's pretty good.

[+1] [2009-09-09 12:15:26] Arjan

browser.urlbar.matchOnlyTyped = true

Combined with the Awesome Bar [1] which, after using it for some time, indeed learns the URLs you visit most, this avoids showing a huge list of URLs. Like for Super User only would show, instead of all links I ever clicked on this site.

(I know many find the Awesome Bar really horrible [2], and so did I. But using matchOnlyTyped and giving it some time to learn my habits, I find it's working quite good after all. However, it does require me to hit Cmd-L/Ctrl-L and hit Return every now and then, to add new URLs to the list.)


[+1] [2009-07-20 02:03:45] Axxmasterr


Very useful if you want more real estate while still being able to use your bookmarks

Can't find it in 3.5.1 - Eduardo Molteni
..And creating a new boolean value crashes FF - Eduardo Molteni
It seems to be a chrome.css tweak and not an about:config setting. - Xenorose
[+1] [2009-09-21 22:24:25] crazyj

For OS X users: accessibility.tabfocus = 3 allows you to tab into ALL form elements, not just text fields.

[+1] [2009-08-19 14:06:33] pramodc84


Default: True

Modified value: False if you want to disable the session restore function

[0] [2009-09-21 21:20:01] JD

network.proxy.socks_remote_dns [1] If you are using a proxy to hide your tracks make sure this is set too so the DNS lookups go through the proxy as well.


[-1] [2009-07-17 04:23:38] jtbandes

config.trim_on_minimize [1] helps keep memory usage down.


(3) Not sure if it's a good idea to set it... it keeps "memory" usage down by swapping to disk, which slows it down. The article recommend leaving it at "false" unless you're running out of RAM. - EMP
Yes, I've seen a few people do tests on it (informal, but still), and it was on average 2 hours of minimized time before it'd crash on restore. Unless you really need the RAM, I reccomend not. - Phoshi