A freshly installed copy of Firefox is a great software package, but what makes this open-source browser so special is the ability to customise 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.

Tools for taming the web

StumbleUponFirst, 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

Gmail Manager & Yahoo Mail Notifier These two extensions do basically the same thing, each for its respective webmail 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:

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

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.

Version reviewed:
Visual improvements

Firefox Showcase A great extension both because of its usability and because it takes away one feature advantage that Internet Explorer 7.0 has over Firefox: the ability to display thumbnails of all open windows and tabs.

Once you install the extension, you'll have a new Showcase submenu under the View menu. From here you can choose to show thumbnails of all tabs in the current window or all tabs in all windows. (IE7, incidentally, only shows thumbnails of the tabs in a particular window.)

Additionally, you can choose to show these thumbnails in a new tab or in a floating window.

You also get new options under the Sidebar submenu: a choice to open tabs from the current window, or from all windows, in Firefox's sidebar. No matter how you choose to display the thumbnails, once you do, clicking on one of them takes you to that window/tab combination.

In some ways, this extension is too complex for its own good. You can safely ignore most of the options and just use the extension in its default configuration.

If you habitually find yourself awash in open tabs, clicking around looking for the page you need, Firefox Showcase will save you a lot of aggravation.

Version reviewed:

Cooliris Previews This interesting extension allows you to preview a Web page before clicking off the one you're on. After installing Cooliris Previews, a small blue icon will appear next to any link you hover your mouse over. Slide the mouse over to that icon and a window pops up containing the destination page. For all intents and purposes, you're on that page, except if you move the mouse off the icon and the pop-up window, the preview vanishes.

At the top of the pop-up window are some additional icons that let you lock the window open, open the preview into a new tab, email it to a friend (although this requires registration at the Cooliris website), close the window or use a Back button. (You can surf around in the preview window, hence the Back button.)

It is in some ways more neat than useful, but for certain sites, such as YouTube, the preview is enhanced. If you preview a link to a YouTube page, only the video opens in the preview window.

In addition to the Preview feature, Cooliris adds a context-sensitive search feature to the right-click menu. Highlight a word or phrase on a page, right-click, choose Cooliris Search and select either thefreedictionary.com, Google Images, Google Search or Wikipedia to search on the highlighted term. If you hover the mouse pointer over any of these four selections, the results will display in a preview window. If you click, they'll open in a new tab.

If you find the preview icon is getting intrusive, you can easily disable previews by clicking an icon in the status bar. You can also disable/enable previewing on a site-by-site basis.

Version reviewed: 2.1

Colorful Tabs & ChromaTabsColorful Tabs is pretty basic. It colors each of your tabs using lovely pastel colors. After a long day of research, this becomes more than just something pretty and can make life easier on tired eyes.

The version reviewed requires Firefox 2.0 or later. Version 1.4 of Colorful Tabs will work with earlier versions of Firefox. See the link for more details.

Version Reviewed: 1.9

ChromaTabs is in many ways similar to Colorful Tabs. The difference is that ChromaTabs determines a tab's colour based on the hostname in the URL. For instance, any tab displaying a PC Advisor page might always be a light green color. If you surf away to a different site, the tab's colour will change.

ChromaTabs looks similar, but its tab colours are assigned based on domain name.

Version reviewed: 1.0

It's a personal preference, really. Colorful Tabs assigns tab colour at random, and as long as a tab stays open, its colour remains the same, no matter where you surf. With ChromaTabs, the colours shift (and some might not be very appealing), but after a while you can tell at a glance where a PC Advisor page is loaded just by scanning for that particular colour.
Matters of convenience

Google Browser Sync & Foxmarks Bookmark Synchronizer If you use Firefox on more than one computer, you might be frustrated keeping track of what bookmarks are where. Google Browser Sync to the rescue. Using your existing Google account, Google Browser Sync will sync not only bookmarks, but sessions, persistent cookies, passwords and history among instances of Firefox on different machines. (This is user configurable on a broad scale - in other words, you can choose to sync cookies, or not to sync cookies, but you can't make the decision based on individual cookies.) In addition to your Google account name and password, you'll assign a PIN to add additional security to the transaction.

Version reviewed: 1.3.20061031.0

One down side is that the initial sync can take quite a while, and for some folks, Google Browser Sync might be overkill. If all you want to do is sync bookmarks, try Foxmarks Bookmark Synchronizer. You'll have to set up an account with Foxmarks (the same is true of Google, but many of us already have Google accounts), but the initial sync seems much faster.

As a bonus, you can access your bookmarks by navigating to my.foxmarks.com. This could be handy if you're on a borrowed machine somewhere.

Version reviewed: 0.84

Session Manager A handy utility to help you manage your Firefox tabs. If you're a web surfer who habitually visits the same sites every morning, all you need do is open the sites in separate tabs and/or windows, and then use Session Manager to save the session under a name of your choosing. After that, every morning start up Firefox and go to Tools, Session Manager, pick your session and voila, all the windows and tabs open up just as you saved them.

You can also choose a saved session as your 'Start Session' (instead of just using a start page) that'll open each time you launch Firefox. As an added bonus, Session Manager tracks your sessions as you surf, and if Firefox (or your system) crashes, you can recover the selection of tabs you had open when it crashed.

One last perk: if you accidentally close a tab, you can easily reopen it from the Session Manager menu.

While Firefox 2.0 has incorporated many of Session Manager's functions, I find Session Manager performs its tasks more elegantly and reliably. And if you're still on Firefox 1.5, Session Manager remains your lone option for these features. Note that the most current version of Session Manager requires Firefox 2.0 or later. Earlier, Firefox 1.5-compatible versions can be found on the Web site.

Version reviewed:

All-in-One Gestures This is one of those extensions that does more than you'll probably ever need, but the core function is to assign commands to 'gestures' made with the mouse. For instance, holding down the right mouse button and dragging the mouse a bit to the left issues a back command. A right-mouse button/dragging up combo opens a new tab. And so on.

There are more than 90 commands available, and the gesture to trigger each is user-configurable. Will you ever remember 90 different gestures? Of course not. But find the commands you use often and assign each a gesture; you'll save yourself miles of mousing.

The extension also provides auto-scrolling, as seen in Internet Explorer. This is where you click the middle button, then move the mouse up or down to start the page continuously scrolling. The farther you move the mouse, the faster the page scrolls.

All-in-One offers a wide selection of small navigation improvements like these. It's really one of those "you have to try it to appreciate it" extensions. But the core functionality of accomplishing frequent tasks via a small twitch of the mouse makes this a must-have for its many advocates.

Version reviewed: 0.18.0

IE Tab It's a fact of life that there are still websites out there that require (or work better with) Internet Explorer. IE Tab to the rescue. Once installed, it places a small icon in your status bar. Clicking this icon swaps out the rendering engine from Firefox's to Internet Explorer's. In my experience, this is particularly helpful with sites that refuse to play video in Firefox.

You can set filters so that certain sites are always displayed in an IE tab. In fact, the extension comes preconfigured with filters for the Microsoft Update site. It also adds an 'Open Link in IE Tab' option to the right-click context menu of Firefox.

Since the extension uses IE's engine, this one is for Windows only.

Version reviewed:

Download Statusbar You're probably familiar with that sometimes-pesky Downloads window that pops up whenever you download a file in Firefox. Download Statusbar suppresses that window from popping up, and instead provides you the same information in the status bar at the bottom of the browser window. (You can still manually open the Downloads window if you find you need it.)

You can roll your mouse over the filename and get a pop-up tool tip with some extra information about your download, too (where it's being download from, and where it's being saved to, the speed of the download, percentage complete and so on).

An additional feature, still in beta, is to automatically run your virus scanner against downloaded files.

Pretty simple, but it helps to 'clean up' the browsing experience. By the way, this is from the same developer as Download Sort, below.

Version reviewed:

Download Sort If you find yourself doing a lot of 'Save Link As' or 'Save Image As' downloading, then Download Sort will be quite a timesaver. It allows you to file downloads by extension, or by a keyword or regular expression in the URL.

Here's how it works. After installing the extension, you set up filters. As an example, you might want any file with the extension .jpg to go into a Pictures folder and anything ending in .zip to go into an Archives folder on your drive.

Now when you right-click on a .jpg image and choose Save Image As, the image immediately downloads into your Pictures folder without any prompting. Right-click on a link to a .zip file and choose Save Link As, and again, the file goes right into your Archives folder. You can optionally have the extension create subdirectories according to date, domain and a few other criteria.

The big drawback here is that Download Sort doesn't intercept normal left-click downloads. It'd be great to see the developer add this capability.

Version reviewed: 2.5.7

Nuke Anything Enhanced If you find yourself printing a lot of web pages, this extension will help you save on ink. Once installed, it adds a 'Remove this object' option to the right-click context menu. Place your mouse over information you don't need printed (menu bars, big graphical logos and so on) and use 'Remove this object' to zap them temporarily. Clean up the page, then print just what you need.

It can be a little fussy, since you don't know exactly what you're hovering over. Images are pretty straightforward, but menus and other page parts can take some trial and error. There's an "Undo Last Remove" option in case you accidentally zap something you need. Or you can just reload the page to restore it to its original state.

One limitation is that you can't easily nuke Flash content, since when you right-click on Flash, you get its context menu, not Firefox's. Sometimes you can find the container tag that holds the Flash, but it can take some trial and error.

Version reviewed: 0.54
Information gatherers

Forecastfox puts an up-to-date weather forecast in Firefox's status bar. Just click one of its icons to see the full weather report at AccuWeather.com.

A wide range of options gives you control over how much, or how little, information you want, including a radar image button, severe weather warnings and extended forecasts of up to eight days. You can set up profiles, each with its own set of options. Use these to get the weather in different post codes if you're a traveller, or create profiles with lots of data for turbulent winter conditions and minimal data for warm, sunny summer days.

The only downside here is that, as with all extensions that rely on data from external websites, if the AccuWeather.com site isn't responding, you won't get any weather updates.

Version reviewed:

Answers This one's simple: Just hold down the Alt key (Option key on a Mac) and click on a word, and a window will pop up with information about that word from Answers.com. (You can have the results displayed in a full window if you'd rather.) There's a More button in the pop-up that'll open a new tab with the full Answers.com results page.

For phrases, you still have to highlight, right-click and choose 'Look up on Answers.com' to get results in a new tab.

Version reviewed: 2.2.22
Web Developer Essentials

FireFTP Why bounce between applications when you can use FireFTP and have a full-featured FTP client in one tab, and the page you're working on in another?

FireFTP adds an option to Firefox's Tools menu. Click on it and a new tab opens (you can set this to a new window if you prefer) with a traditional two-panel FTP client: local files on the left, remote on the right. By right-clicking on files you can tweak their permissions and all the other things you'd expect to be able to do via FTP.

One nice feature is 'View on the web', which opens the file on the remote server in a new tab. You can set up each host to "snip" out parts of the directory structure (/public_html, for example) so that you get valid URLs rather than the full "physical" path to the file.

The one disappointment is that the client is FTP only. When asked about SFTP support, the author responds (in a FAQ on his page), "Maybe in Version 2.0." Let's hope.

Warning: the combination of FireFTP and Firefox exposes a regression bug in Firefox, causing high CPU usage. If you're still running, you should upgrade to before installing FireFTP.

Version reviewed: 0.94.6

Firebug is an essential tool for developers working on web pages. It allows you to examine and tweak the HTML, CSS and JavaScript contained in a page, all on the fly. Firebug opens either as a panel at the bottom of the page you're inspecting, or in a separate window.

Exploring all that Firebug can do could be a full article of its own. But for a taste of its power, let's look at basic HTML coding. Once Firebug is activated, running your mouse over an HTML tag in the Firebug window causes a highlighted area to appear on the rendered page, showing where that tag is in the display.

Alternatively, you can put Firebug in Inspect mode. Then running the mouse over the rendered page causes the appropriate line of code to be highlighted. By double-clicking that code, you can edit it and see your changes on the fly. CSS works in much the same way.

For JavaScript development, Firebug finds errors and quickly jumps to where they are in the code. You can change the code and step through a script line by line, set breakpoints and so on. Essentially, it's a full-fledged JavaScript debugging system residing in a browser extension.

Firebug is a great extension and a big topic. If you develop web pages, you'll want to add this extension to your tool kit. There's plenty of documentation and discussion of what it can do at the GetFirebug website.

Version reviewed: 1.01

Web Developer is another virtual Swiss Army Knife for coding. There's some overlap with Firebug, but where Firebug concerns itself almost exclusively with the content of a web page, Web Developer offers tools to tweak how you're interacting with the page.

For instance, you can modify cookies on the fly, examining, deleting and even manually adding them. You can tweak form settings, clear private data and disable the cache - all kinds of real-time manipulations.

Web Developer's features can be accessed as a tool bar, or as cascading menus under Firefox's Tools menu. The tool bar is particularly handy since you can see all 12 of the top-level categories of features at a glance (and, of course, it can be easily turned off when you're not in the midst of site development).

This extension can even be useful for regular web users, thanks to features like the ability to turn off background images. If you've ever struggled to read text displayed, for example, over a background image of someone's dog, you'll appreciate this.

Web developers will probably want to run both Firebug and Web Developer, and the two extensions seem to co-exist peacefully.

Version reviewed: 1.1.3

MeasureIt So simple and so useful. After installing this extension, you'll have a small ruler icon in your status bar. When you click on this icon, the client area of your browser window will fade out a little, and you'll have a crosshair cursor.

Use this to drag out a box over a section of the screen. Next to the box is its height and width, measured in pixels. No more guessing as to how wide a sidebar really is, or if the footer is really rendering 150 pixels deep like your style sheet says it should. When you're done, a tap of the Escape key turns off MeasureIt and gives your web page back to you.

Version reviewed: 0.3.6

ColorZilla Another quick and simple tool, this one more for designers than developers. ColorZilla puts an eyedropper icon in your status bar. Click it and you'll get a crosshair cursor. As you run this over a web page, the RGB values of the pixel under the crosshair will display in the status bar, both as three separate values and as a hex value (such as R:255, G:255, B:255 | #FFFFFF).

Additionally, you'll get a border around the style container you're hovering over, an indicator of what the container is and what style it is using (h2.posttitle or div#content, for example).

ColorZilla also offers a colour picker, colour palettes and easy access to DOM Inspector, a Mozilla tool for examining a page's Document Object Module.

Version reviewed: 1.0

This blog first appeared on our sister site PC Advisor

Peter Smith is a web developer and freelance writer with a special interest in personal technology and digital entertainment.