Greasemonkey is the handiest Firefox extension ever.

It lets you maintain a set of DHTML scripts which are applied to some or all webpages you view to change its behavior and content. The scripts are written in Javascript. This may not give you a clear idea of what it does; suffice to say it lets you fix things about webpages that you think are broken. For example, I’ve got user scripts installed to do all of the following:

  • ununderline: Convert all non-link underlined text to italics, so only links are underlined
  • Linkify: Convert all text URLs to clickable links
  • Livejournal userpic adder: shows LJ userpics when you mouse over a Username
  • skin 2: different look for
  • ALT tooltips: makes Firefox show an image’s alt attribute on mouseover when there is no title attribute
  • Newsmasher: adds a floating link at the top of every page which brings up a floating iframe containing the posts for a URL, so you can read other people’s comments about it
  • Friend of Print-Friendly: takes you directly to printer-friendly pages on a whole bunch of websites
  • Expand Area: lets you drag the corner of a textarea to make it bigger (this one is a great example of how flexible and useful greasemonkey is)
  • Check Range: lets you check a range of checkboxes by clicking one at the beginning and then shift-clicking one at the end of the range
  • Salon Auto-Pass: bypasses the Salon daypass requirement
  • Metafilter deleted posts: shows links to deleted posts on Metafilter

I’ve written a couple of user scripts already:

  • SourcePlease: rewrite sourceforge download URLs to point directly to a file instead of their “Choose a mirror” page
  • HTTP-Be-Gone: remove the example “http://” from form fields that expect a URL, so you don’t have to see “http://http://” after you paste

There’s another hundred or two user scripts available on the GreaseMonkey wiki — reading through the list there will give you an idea how great this thing is. I never really found user CSS that useful, but being able to fix webpages to work the way you like is incredibly handy.

3 responses to “Greasemonkey”

  1. greasemonkey, while very sexy, increased my page load time dramatically. maybe i was using some very poorly written handlers.

  2. Yeah, I bet it’s pretty easy to do things wrong. I don’t notice it here even with that pile of stuff loaded. I suspect that of my two, SourcePlease is one done the right way, and HTTP-Be-Gone is one done the wrong way. :-)