Greasemonkey: Yet Another Reason to Use Firefox

Ever used a new technology product and felt like a little light bulb really has switched on above your head? That's the sort of epiphany I went through earlier this week, when I started using Greasemonkey, an utterly brilliant extension for the Firefox browser.

Simply put, Greasemonkey (which has been around since late last year) allows you to change the functionality of Web sites on the fly--adding new features, stripping out existing ones, and otherwise tweaking a site in ways its operator never intended. If you're a Web geek, you may do this customization by writing Greasemonkey "user scripts" (which are snippets of DHTML code) yourself. The rest of us will install canned scripts written by other folks--there are scads of them out there for major sites, and they're all free.

A Greasemonkey script can do something mundane such as strip the ads off the pages at a site such as Google. But it can also customize sites in ways that make them more convenient to use. Click the play button on the screencast below (which I created with Camtasia Studio) to see how one Greasemonkey script streamlines Google Image Search.



Here's another screencast of a much more ambitious Greasemonkey user script that adds a truly useful feature to Gmail--the ability to save searches so that you can execute them with a single click at any time:



And no, I'm not completely fixated on Google. Here's a closeup of Book Burro, a slick script that notices when you're on an book-shopping site such as Amazon or Barnes and Noble. When you click on it, this tool polls other book sites and lists their prices for the book you're looking at. (Sound like adware? Not really, since Book Burro isn't a commercial tool, and it operates entirely at your discretion and can be turned on or off with one click.)



One of the great things about Greasemonkey scripts is that so many of them make nitpicky changes to the user interfaces of well-known sites; you get a really tangible sense that the script authors are fixing something that annoyed them personally. For instance, one script does nothing more than clean up the notoriously hideous font formatting on movie gossip site Aint-It-Cool-News.com.

At the moment, there are Greasemonkey scripts for 149 sites (from About.com to Zap2It)...oftentimes, bunches of them for one site. (If you installed every Greasemonkey script for Google, you'd reinvent it into a significantly different--and, arguably, better--place.)

Other scripts work are designed not for one site but for universal use; I tend to find these less compelling than their site-specific brethren. But I do admit to being fascinated by one script which adds Google text ads to every site you visit.

Greasemonkey may be brilliant, but that doesn't mean that it, or the scripts it runs, are perfect. For one thing, some of the scripts I tried just didn't work, and I suspect that some that run fine now will break the moment the sites they're designed for get changed.

There's also been some discussion of whether Greasemonkey poses a security threat, since it can make seamless, subtle changes to how a Web site works. I don't think there's a big problem here, since you need to install both Greasemonkey itself and individual user scripts before they can have any effect on your browsing. But I do wish that Greasemonkey alerted you to the fact that it's altering a particular page. (You do get a cute li'l monkey icon in the lower right-hand corner of your Firefox window, but as far as I can tell, it only tells you if Greasemonkey is on or off, not whether it's rejiggering the page you're on.)

The beauty of Greasemonkey is the big-picture idea here: Armed with the right scripts, you can mod the sites you use to make them operate the way you want. Your Google and Amazon may end being a little different from my Google and Amazon...whether Google and Amazon want it that way or not.

Greasemonkey is fun and useful right now--and, like the title of this post says, it's a big reason to opt for Firefox as your primary browser. But I think the scripts we'll see six months or a year from now will be even more inventive, and that this form of grass-roots site customization will have a real impact on the way folks use the Web.

In fact, we're already starting to see its influence elsewhere. Opera 8 has a similar feature with some degree of Greasemonkey compatibility, and there's a project with the amusing name of GreasemonkIE that's working to bring user scripts to IE.

Anyhow, if you're intrigued by all this--and I hope you are--the Mozilla site has everything you need to start using Greasemonkey.