by Gina Trapani

Click to viewThe Firefox homepage calls the web browser "fully customizable to your online life," and that's not just marketing claptrap. Beyond the extensive options available in its menus and dialogs, there's a lengthy set of advanced Firefox preferences that can customize the browser to your specific needs. Sure, your brother-in-law's not likely to edit Firefox's default configuration, but you? You're a power surfer and you want your web browser your way.


In honor of the Firefox 2.0 release yesterday, today we'll dive deep into the bowels of the fox's config with a handful of my favorite Firefox 2 (and older) tweaks.

Firefox 2 officially released As we reported yesterday, Mozilla officially released Firefox 2 today along with a nice new revamp… Read more


How to modify Firefox's configuration (about:config)

All this "advanced config" talk got you worried? Fear not, my friend. Here's the deal: Firefox's configuration is a long list of keys and values. To view this list, type about:config into the Firefox address bar. Then, enter the name of the key you want to update in the "Filter" field. The list will narrow to only the entries that match your keyword as you type, as shown.

(The key, of course, is knowing the key. More on that below.) To modify the value of a key, double-click on the value field and update the entry. To see your changes, restart your browser. Easy as pie.


Got it? Good. Let's get to tweaking.

Session restore

Fx 2.0 only: As a blogger and web mail user, it breaks my heart to recount how many times I've composed a long post or email message, then accidentally closed the tab or browser and lost all my work. No more! With Firefox 2, set the browser.startup.page key to 3 to restore your browsing session - with form entries intact! - every time you start your browser or undo close tab after a wayward click. Note: By default, Firefox 2 automatically restores your session if your browser crashes - but this does it every time you restart your browser normally. Thanks for the tip, Arun!


Key: browser.startup.page

Modified Value: 3

Default: 1 (open your specified homepages)

Update: Ryan points out that doing it this way is like swatting a fly with a sledgehammer. To do it the normal person way, from the Tools menu choose Options, and in the Main area, select "Show my windows and tabs from last time" from the "When Firefox starts" dropdown. D'oh! Thanks Ryan!


Tab width before scrolling kicks in

Fx 2.0 only: The biggest interface changes in Firefox 2 involve tabbed browsing. Power surfers who open more than a dozen tabs will notice that Firefox 2 minimizes tabs to a certain width, then sets the excess to scroll off the tab bar with left and right arrows. As someone who often has more than a dozen tabs open, not being able to see them all made me crazy. One solution is to reduce the minimum tab width so that more tabs fit in the bar before the scroll kicks in. The default is 100 pixels; I found that 75 worked better for me - page titles were still readable, but more tabs could fit. Compare 100 width, which fits 7 tabs across at this size (click to enlarge):


To 75, which fits 10 across at this size (click to enlarge):


To disable tab scrolling entirely, set the value to 0.

Key: browser.tabs.tabMinWidth

Modified Value: 75 (fit in more tabs before overflow enables scroll)

(fit in more tabs before overflow enables scroll) Alternate Modified Value: 0 (disable scroll entirely)

(disable scroll entirely) Default: 100

Tab close buttons

Fx 2.0 only: Another tab interface change in Firefox 2 is the addition of a close button on each individual tab. I happen to love this, but some hate it, saying it causes them to accidentally close a tab when just trying to switch to it. If you're a hater, revert to the Firefox 1.5 behavior by changing the browser.tabs.closeButtons value to 3. This will not display close tabs on individual tabs, and turn on a single close tab button at the right end of the tab bar.


Key: browser.tabs.closeButtons

Modified Value: 3 (revert to Firefox 1.5 behavior)

(revert to Firefox 1.5 behavior) Alternate Modified Value: 2 (don't display any close tab buttons)

(don't display any close tab buttons) Default: 1 (display close buttons on all tabs)

Fetch only what you click

Fx .6 and up: Firefox has this wacky little feature that downloads pages from links it thinks you may click on pages you view, like the top result on a page of Google results. This means you use up bandwidth and CPU cycles and store history for web pages you may not have ever viewed. Creepy, eh? To stop that madness, set the network.prefetch-next key to false.


Key: network.prefetch-next

Modified Value: false

Limit RAM usage

All versions: Goodness knows I've done a good amount of belly-aching about Firefox's voracious appetite for RAM. (It's consistently the most memory-intensive process on both my PC and Mac.) Happily a simple config tweak got Mem Use right back down to a more comfortable number. Along with the previous prefetch mod, set your browser.cache.disk.capacity browser.cache.memory.capacity to a value that fits your total RAM.


Key: browser.cache.memory.capacity Modified Value: Depends on your system's total memory. According to Computerworld:

For RAM sizes between 512BM and 1GB, start with 15000. For RAM sizes between 128MB and 512M, try 5000.


Turn off chrome tooltips


All versions: I have an irritating Firefox problem on my Mac. When I try to drag a bookmark into one of my bookmark toolbar folders, the tool tip gets in the way and prevents the drop from working. Argh! Like you, I already know what all the buttons on my browser chrome do, so the tool tips aren't necessary. To turn them off, set the browser.chrome.toolbar_tips key value to false. Bonus is, it solved my Mac's bookmark drag and drop problem.

Key: browser.chrome.toolbar_tips

Modified Value: false

Lastly, though 2.0's default value is a lot more reasonable than 1.5's, you can use about:config to put off that annoying Unresponsive Script dialog on Javascript-heavy web pages.


Update: From the comments, a few more good about:config tweaks:

layout.spellcheckDefault = 2 turns on Firefox 2's spell-checking in input fields as well as textareas. (That means no more typos in Lifehacker post headlines!)

turns on Firefox 2's spell-checking in input fields as well as textareas. (That means no more typos in Lifehacker post headlines!) browser.urlbar.hideGoButton=true turns off the rarely-used Go button at the end of the address bar, for more room to see long URLs. Thanks, sister-ray


See the MozillaZine about:config wiki page for the exhaustive list of Firefox preferences keys, their possible values and effects.

What are your favorite Firefox about:config tweaks? Post 'em up in the comments.

Gina Trapani, the editor of Lifehacker, is a sucker for advanced settings. Her semi-weekly feature, Geek to Live, appears every Wednesday and Friday on Lifehacker. Subscribe to the Geek to Live feed to get new installments in your newsreader.