20 must-have Firefox extensions

A freshly installed copy of Firefox is a great software package, but what makes this open-source browser so special is the ability to customize it via extensions and themes to really make it yours. The problem is, there are so many available add-ins, it's tough to know what's worth installing and what's just going to junk up your system.

That's where we come in. We've ferreted out 20 of the best extensions and add-ins used and recommended by hardcore Web surfers, developers and IT pros. Whether you're looking for more streamlined surfing, improved look and feel, cool design tools or serious Web development help, there's something (and more than likely several things) here for you.

Don't miss our related story,

Top 10 Firefox extensions to avoid.

And while we've dug deep, we're sure we've missed some gems. So please be sure to share your favorite extension in the comments at the bottom of the page.

Tools for taming the Web

StumbleUpon

First, a warning. StumbleUpon is hazardous to your productivity! StumbleUpon is one of these social networking Web applications that are becoming so popular lately. This one provides a way to find new Web sites that you may find enjoyable or useful.

This extension adds a StumbleUpon tool bar to Firefox. You can get to all the core functionality of StumbleUpon via this tool bar, including setting up an account. You pick some initial categories of the kinds of sites you're interested in (a few examples: Ancient History, Humor, Self-improvement) as part of the sign-up process, and can always tweak these later.

Once everything is set up, you click the Stumble! button in the tool bar to be taken to a random site that has something to do with your categories. If you don't like the site, click the Thumbs Down button. If you do like it, click Thumbs Up. The more sites you rate, the better your Stumbles will match your tastes. If you rate a site that isn't in the StumbleUpon database yet, you can enter some basic information about it so others can stumble onto it.

StumbleUpon isn't all that practical, but it is fun and can transport you back to the days when just idly surfing the Net turned up all kinds of interesting things.

Version reviewed: 2.91

addons.mozilla.org/firefox/138

Gmail Manager & Yahoo Mail Notifier

These two extensions do basically the same thing, each for its respective Web mail service.

The Yahoo Mail Notifier is fairly basic; it just puts a small mail icon in your status bar and indicates how many new messages are in your Yahoo mail account. It'll display a little pop-up to catch your attention if you want it to. Clicking the icon takes you to Yahoo mail.

Version reviewed: 0.9.9.2

addons.mozilla.org/firefox/1264

The Gmail Manager does all this and more. If you hover your mouse over it, you'll see the total number of new messages, how many spam messages you have, new message counts for all your labels and how much space your mail is taking up. Below all that is a listing of your most recent 10 messages, showing From, Subject and first line of the body of the mail (you can turn all this off). It also supports multiple Gmail accounts, and you can set it to cause all mailto: links to open up a Compose New Message window in Gmail.

Version reviewed: 0.5.3

addons.mozilla.org/firefox/1320

Sorry, Hotmail users. I wasn't able to find a notifier for you.

Greasemonkey

Let's get this out of the way right up front: Greasemonkey is not for the faint of heart. It basically allows you to add JavaScript to any Web page, but writing these scripts requires a good knowledge of scripting. The good news is that there are many generous souls out there who share the scripts they create.

When first installed, Greasemonkey does nothing. It just enables the scripting. You'll have to write, or install, scripts before you see any changes on your pages.

So what do these scripts do? Almost anything you can do with JavaScript. For example, I use both Google's Gmail and Reader services. I found a script that causes Reader to appear on the same page as my Gmail. That's a pretty big change. (It's easy to disable a script, and even easier to universally disable Greasemonkey, in case you need to undo a change.)

Then there are lots of scripts that do small things like remove the Edit features from Wikipedia. Most of us are never going to edit these pages, so why not clean them up a bit? Another script, shown here, makes Google search results appear in two columns to provide better use of space on wide monitors. The possibilities are endless.

Check out userscripts.org for a script repository. If you want to write your own scripts, try diveintogreasemonkey.org or pick up Mark Pilgrim's Greasemonkey Hacks from O'Reilly Media.

Version reviewed: 0.6.7.20070131.0

addons.mozilla.org/firefox/748