Bookmarklets: The Baby Extensions

Firefox is designed to be simple but extensible. If you want a feature that isn't included, odds are you can install it in under five minutes. Usually, you would do this by installing an extension and restarting Firefox, as I outline in Chapter 20. However, some smaller features are available as bookmarklets, which require no installation and no restart. These mini-extensions are so named because you access them just like you would a bookmark.

Bookmarklets are easy to use but difficult to explain, so the best method is to dive right in. You can use the following steps to obtain a bookmarklet that zooms in on a Web site's images:

1. The Bookmarks Toolbar is visible by default.

2. Navigate to Jesse Ruderman's Web site at http://www.squarefree.com/bookmarklets.

   Jesse is a tester on the Firefox team who has compiled a large assortment of bookmarklets. Jesse's bookmarklets are divided into categories based on function.

3. Click the Text and Data Bookmarklets link.

   The page that loads contains a list of bookmarklets (in the leftmost column) and a description of each (in the middle column).

4. Drag the Zoom Images In bookmarklet out of the page and onto your Bookmarks Toolbar.

5. Click the newly created Zoom Images In button on the Bookmarks Toolbar.

When you click the button, the images on Jesse's Web site grow. If you click it again, they grow even larger. This isn't a permanent change. When you reload the page or visit a new page, the images are restored to normal size. Indeed, one reason bookmarklets are considered mini-extensions is that their effects are only temporary. This is also why they're so much easier to install than extensions: they can't have any long-term effects, so the risk of using them is much lower.

If you don't want to keep this zoom bookmarklet, you can delete it from your Bookmarks Toolbar just as you would delete a regular bookmark: Right-click it and choose Delete. Note that bookmarklets can reside in a regular bookmarks folder instead of on the Bookmarks Toolbar, but they're easier to access from the toolbar. Also, if you put a bookmarklet in a folder, Firefox tries to load the bookmarklet in a tab when you choose the Open in Tabs option (see Chapter 5), which can lead to some funky (but generally unharmful) results. This is a bug we developers hope to fix in a future release.

Tip 

Be sure to explore the rest of Jesse's bookmarklets. You can test a bookmarklet before deciding to drag it to your Bookmarks Toolbar just by clicking it, and reloading the page always undoes its effects. Some of the bookmarklets are fairly technical in nature, but none are permanent — so feel free to experiment!