Ultimate Collection of Best “about:config” Tweaks for Mozilla Firefox

We have posted several interesting and useful about:config tweaks for Mozilla Firefox in past. Most of these tweaks add extra functionality to Firefox and some of them tweak the performance of Firefox.

Recently an AskVG reader "Memo" sent us following email:

Hello Dear Vishal:

As we know Firefox 4 is out there; however there are thousands of guides/tutorials to enhance its performance through "about:config" tweaks. Many of these tweaks apply for FF3.xx; additionally, many of those are made on a general basis which does not apply for all machines. In summary, it is a total mess.

Therefore, I ask you to make one; a powerful one; one that uncover the mysteries of Firefox 4; the only one to find; the only one that really works; the only one to rule them all.

As a young Hobbit, your heart's pureness, honesty and wise make you the only one to trust, the only one to follow such a difficult task to get us out from darkness and slowness and get our Firefox invincible.

I know there is a post about it, but it was not made by you, even more it contradicts other opinions expressed by other experts and/or sources.

Please do it, and immortality will be yours.

All the best


So today we decided to create this dedicated topic which will contain all special and best about:config tweaks for Mozilla Firefox 4.0 and later versions.



1. Make sure Firefox is not running. Now type following in RUN or Start Menu search box and press Enter:


2. Now you'll see a folder xxxxxxxx.default. Open it.

3. Look for a file "prefs.js". Right-click on it and select "Edit" option.

4. Copy and paste the tweaks mentioned in "ULTIMATE COLLECTION OF TWEAKS" part at the end of the file.

5. Save the file and restart your browser.


1. Open Firefox and type about:config in the addressbar and press Enter. It'll confirm, click on I'll be careful, I promise! button.


2. Now type the preference's name (mentioned in double-quotes in "ULTIMATE COLLECTION OF TWEAKS" part) in the Filter box, it'll show the key in results.

3. Set its value as mentioned by double-clicking on it.


Almost all preferences are boolean and contain value of True/False or 0/1. If you want to change the functionality or want to reset them to default, simply change true to false or 0 to 1 and vice versa.


Following is a small description of each preference respectively:

  • Enables Internet Explorer look-like Quick Tabs feature [Link]
  • Enables new ctrl+tab preview thumbnails list [Link]
  • Disables automatic virus scanning in built-in download manager [Link]
  • Disables toolbar auto-hide function in full screen mode [Link]
  • Disables animation while going full screen [Link]
  • Disables animation in Tab groups (Panorama) [Link]
  • Enables cool animation in Preferences/Options window [Link]
  • Brings back Save tabs and quit feature [Link]
  • Disables animation while opening new tab [Link]
  • Disables automatic main window closing when you close last tab [Link]
  • Disables open new tab after current tab feature [Link]
  • Disables automatic text selection upon single clicking in addressbar [Link]
  • Enables text selection upon double-clicking in addressbar [Link]
  • Enables built-in spell checker to work in text boxes and web forms [Link]
  • Enables Secret "Click and Hold Context Menu" Option [Link]
  • Instant Applies Preferences without Closing Options Window [Link]
  • Shows Tabs Below Orange Button When Firefox is Maximized [Link]
  • Enables Secret "Middle Click to Paste Clipboard Content" Feature [Link]
  • Disables domain name highlighting in gray color in addressbar (Thanks NZero & Prateek)
  • Re-enables http:// URL prefix in addressbar (Thanks NZero & Prateek)
  • Disables delay time while installing add-ons (Thanks TheAslan)
  • Changes number of rows in new tab page [Link]
  • Changes number of columns in new tab page [Link]


user_pref("browser.allTabs.previews", true);
user_pref("browser.ctrlTab.previews", true);
user_pref("browser.download.manager.scanWhenDone", false);
user_pref("browser.fullscreen.autohide", false);
user_pref("browser.fullscreen.animateUp", 0);
user_pref("browser.panorama.animate_zoom", false);
user_pref("browser.preferences.animateFadeIn", true);
user_pref("browser.showQuitWarning", true);
user_pref("browser.tabs.animate", false);
user_pref("browser.tabs.closeWindowWithLastTab", false);
user_pref("browser.tabs.insertRelatedAfterCurrent", false);
user_pref("browser.urlbar.clickSelectsAll", false);
user_pref("browser.urlbar.doubleClickSelectsAll", true);
user_pref("layout.spellcheckDefault", 2);
user_pref("ui.click_hold_context_menus", true);
user_pref("browser.preferences.instantApply", true);
user_pref("browser.tabs.drawInTitlebar", false);
user_pref("middlemouse.paste", true);
user_pref("browser.urlbar.formatting.enabled", false);
user_pref("browser.urlbar.trimURLs", false);
user_pref("security.dialog_enable_delay", 0);
user_pref("browser.newtabpage.rows", n);
user_pref("browser.newtabpage.columns", n);

NOTE: In the last 2 preferences, 'n' represents any number starting from 1. So replace 'n' with your desired number of rows and columns which you want to see in new tab page of Firefox.

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Posted in: Mozilla Firefox

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