Greasemonkey: Firefox Swiss army knife bodes User Empowerment

Greasemonkey seems to be taking the (firefox) web world by storm…

What it is

Basically, it’s “a Firefox extension which lets you to add bits of javascript ( = user scripts) to any webpage to change it’s behavior. In much the same way that user CSS lets you take control of a webpage’s style, user scripts let you easily control any aspect.” (from the Greasemonkey site).

What does it mean

Javascript is incredibly powerful, and more and more sites are designed in such a way that they’re easily “scriptable”. By adding “user scripts” to sites, you can change and add functionality.

How does it work?

Let’s illustrate with an example: the “Google annotate” user script that enhances Google search results with information on available rss feeds and tags on that search result.

1: With Greasemonkey installed, you can simply right-click on a link to a userscript (= a .js file):
Install Greasemonkey user script

2: Modify some options (e.g. adding your local google site):
Configure Greasemonkey user script

3 … and this is the result: search results are enhanced with available rss feeds, link to entries and a tags link showing the used tags when clicked on:
Modified Search results

Some other examples

Enough inspiration at this GreaseMonkey User Scripts Directory:

  • Changing layout:
    • Title Scrubber: removes “Welcome”, “Welcome to”, etc. from title bars.
    • Site skinner: Adds a skin link down the bottom of every page which lets you add custom css to the page (uses cookies to auto load css).
    • Expand TextArea: allows you to resize textareas.
  • Modifying behaviour:
    • Hide Adsense: Hides Google Adsense IFrames
    • Flickr: Degradr: Replaces flickr’s flash-embedded images with actual image files
  • Integrating functionality of several sites
    • Amazon/Melvyl: Check UC Libraries Given a link to Amazon, check Univ. of California’s libraries for availability
    • DeliciousGator: Add post links to News Gator Online.
    • Amazon Linky Inserts three icon links under book titles, one to a price comparison site and two to libraries.


You might have heard about the row on the Googe autolink feature, reminiscent of the Microsoft Smart tags discussion almost 4 years ago. Now grass roots developers have the possibility to do the same with User scripts: automagically changing branding, removing ads, inserting links to other sites… both for specific domains or as general browser behaviour. As a kind of “Sue me if you dare” statement Mark Pilgrim designed Butler: a user script that removes ads from Google search results, and adds links to competitors.
The implications for online business models are huge, and we might see some nasty battles coming up – as well as new services made available via these “scripts in the middle”.


In itself, it doesn’t seem a spectacularly new technology:

The really new thing with Greasemonkey is the ease scripts can be written (javascript has been around for almost 10 years), made available (simply put a file online) installed (right-click), and propagated (think of a user script showing the available user scripts for the site you’re browsing!!). Without any doubt, zillions of these scriptlets will be hacked together and spread like wildfire, extending and bending existing functionality. (see for example Greasemonkey for Google Maps)

A new architecture for the web?

Jon Udell asked whether there could be such a thing as a general architecture of intermediation, a way of devising applications and their connections in such a way that an intermediary layer can adapt their behaviour and combine their data and functionality with that of other applications, even your own private applications. According to Simon Willison, Greasemonkey and its “scripts in the middle” could be a very light-weight implementation of such an architecture. To be continued…

Oh BTW: Greasemonkey for Internet Explorer is underway :-)

Update April 4: Jon Udell’s yesterday screencast explains all of this so much better!

2 Responses to “Greasemonkey: Firefox Swiss army knife bodes User Empowerment”

  1. Cathing loose MP3s with Greasemonkey and Says:

    […] Get Greasemonkey. If you haven’t heard of this Firefox extension (or still don’t see why you’d even need to switch to Firefox!) check out a previous posting on Greasemonkey […]

  2. Master of your mailbox: an email alias for every site you leave your address Says:

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