One of Firefox's important features, as RPGeek notes, is its expandibilty through the use of modular extensions. The following is a big list of extensions that may or may not be useful to you. These mostly come recommended off the SA Forums and The Extensions Mirror.
Since these are mostly based on the interplatform XUL language, they will often work on your crazy hacker open-source GNU/Computer/Machine! Also, on your Mac.
Many of these are not available from any Mozilla Project site. I can't really vouch for the integrity of any of these extensions - you should remember that you are running "arbitrary code", and always use common sense in installing strange software. I don't know of any malicious extensions, but I'm sure we'll see porn dialers, helpful wallet applications, and similar garbage before long. If you suspect any malfeasance on the part of your new extension, remove it and apply virus- and spyware-defeating utilities.
A more benign problem is that not all are well-coded, and some tend to crash your whole Firefox or use way too many computrons. (This seems to have a synergistic effect with Firefox's predilection for memory leak.) Try disabling some extensions if you have performance issues.
Newish additions are highlighted in bold.
- Allow Right-Click (link) Lets you bypass the "protection" from right-click context menus on stupider websites.
- Always Remember Password (link) Some sites tell Firefox not to automatically remember your password to login, citing such limp-wristed nonsense as "security". What do they know that you don't, huh?!?! Stifle that nanny attitude with this extension.
- AutoFill (link) This is a more full-featured form filler than the one built into Firefox, which can behave pretty oddly at times. The author says he wants to replicate Google Toolbar's form filling.
- Bandwidth Tester (link) Tests your downstream.
- Bookmark Backup (link) Backs up the bookmarks file after every session.
- chromEdit (link) This is a nicer interface for editing the profile files such as userContent.css to set preferences.
- ColorZilla (link) This lets you grab the exact color value (RGB) off an element in the page and do some other color-related stuff for web developers.
- Context Highlight (link) Highlights in yellow all instances of a word or phrase on a page.
- Copy Plain Text (link) Gives you the option "Copy as Plain Text" so you lift only the content, not the formating.
- Delicious Delicacies (link) Vital. Restores the cookie placeholder text to the way it was in earlier version of Firefox. DELICACIES 4EVAR
- Ez Sidebar (link) Makes the Sidebar undockable and panel-addable.
- FlashGot (link) This is a robust plugin that adapts Firefox for use with many external download managers.
- ForecastFox (link) Pulls local weather conditions off The Weather Channel's feed; displays said conditions in the status bar. It allows you to say how many days in advance should be forecast and set other little things.
- Greasemonkey (link) This is a cool idea - it runs custom DHTML scripts to dynamically alter the code of pages, meaning you can "easily control any aspect of a webpage's design or interaction". The scripts have to be written on a page by page basis, but there are a lot of great ideas popping up (for instance..)
- IE View (link) In Windows, opens the current site in Internet Explorer, which is helpful for poorly coded sites that don't work in Firefox.
- Image Zoom (link) Lets you zoom in on parts of images. This is useful when people post raw photos from digicams, but your pitiful monitor does not have 5 megapixels.
- Google Send to Phone (link) txt msgs r rly 2 trs imo
- Mozilla Archive Format (link) This gives the option of saving web pages, including all the stuff on the page, in a single file. IE already had this option, using the MHT format. The MAF extension is compatible with MHT, but is apparently better because it uses some XML thing.
- Platypus (link) Experimental plugin that allows you to dynamically rearrange pages as you see fit, via visually rearranging or removing page elements, or running regexps on the HTML. Then the modifications are saved and applied with Greasemonkey. This kind of innovation is what makes extensible applications cool.
- Session Saver (link) One of Opera's killer features. This extension saves the windows and tabs you have open, so when you restart Firefox (or recover from a crash!) you can restore the same configuration.
- SpellBound (link) Spell chequer four forms awn web Paige's. Ported from Mozilla Male.
- StockTicker (link) OH NO NASDAQ IS DOWN THERE GOES RETIREMENT
- SyncMarks (link) Really cool if you're switching computers a lot. Lets you keep bookmarks up to date between browsers, machines, and platforms.
- Translate Page (link) Transforms a page from unreadable gibberish to vaugely English-like babble using Google's page translator.
- Undo Close Tab (link) Come back, closed tab! I didn't mean what I said!
- Web Developer (link) Adds tools like CSS validation and code validation to the menu.
- Adblock (link) Basic image blocker. Allows you to block certain images or embedded Flash movies. It has regexp matching - for instance, I use the string *doubleclick* to block all ads delivered by DoubleClick. There's a detailed writeup on Adblock already, by the way.
- Filterset.G (link) Popular set of filter expressions for AdBlock. This set focuses on low overhead and no false positives, but I find it's pretty comprehensive. Updated weekly, too.
- AniDisable (link) Gives you options for animated gifs - you can have them only play through once, or disable animation.
- Cookie Button (link) Adds a widget to the toolbar allowing you to change cookie preferences for the active site.
- FlashBlock (link) This prevents Flash movies from loading until you click on them. One reason for this is the prevalence of big, obnoxious animated ads - another is the fact that Firefox's popup blocker does not block pages spawned by embedded objects, so it's common to see a 1x1 .swf popup generator. (You can whitelist pages that you want to see the Flash on.)
- SecurePassword Generator (link) Automatically builds secure passwords.
- SwitchProxy (link) Quickly jump between proxy configurations (using Anonymizer, for instance.)
- Add Bookmark Here (link) Puts an "Add Bookmark Here" option in the subfolders of your Bookmarks menu.
- All-in-One Gestures (link) This is a huge extension. It's a superset of the normal gesture extension, but also adds wheel/rocker gestures, autoscrolling, and more customization options than are strictly necessary. This means you can navigate really efficiently if you're willing to put the time in. Hours of fun!
- AutoCopy (link) Select text, and it's automatically copied to the clipboard. This seems trivial, but copying from the web is a really common task.
- Compact Menu (link) Lets you rearrange the menus on the top toolbar.
- Disable Targets For Downloads (link) Gets rid of the blank window that often pops up in Firefox when you try to download something.
- Download Manager Tweak (link) Adds some informative widgets to the Download Manager and lets you dock it.
- Download Statusbar (link) Puts the progress of current downloads in a cute bar at the bottom of the screen.
- Focus Last Selected Tab (link) A simple, intuitive tweak - when you close a the focused tab, focus will shift to the last tab you had open.
- Googlebar (link) Unofficial port of the Google Toolbar for IE, with most of the functionality.
- Google Toolbar (link) Official port of the Google Toolbar for IE. This one has spelling, translation, automatic form filling, et cetera.
- Link Toolbar (link) This is a port of an old Mozilla feature. It lets you browse an associated series of pages quickly. Practically speaking, you can jump right from HotBabe12.jpg to HotBabe13.
- Linkification (link) Converts plaintext URLs to clickable links.
- miniT (link) One of many tab behavior-changing extensions. This one adds scrolling through them with the mouse wheel and lots of other little tweaks.
- miniT(drag+indicator) (link) Drag-n-drop them tabs.
- Mouse Gestures (link) This is the original mouse gesture branch (essentially a rewrite of the Opera feature), which is lighter-weight and less intimidating than the giant all-in-one thing.
- OpenBook (link) Lets you screw with the "Add Bookmark..." dialog, should you find it unsatisfactory.
- Productivity and Networking Information Component (link) This allows you to designate a maximally productive website. Should you feel at some moment that you are functioning below your maximal productivity, you can hit the "PaNIC" key to instantly close all open pages and jump to that highly productive area.
- Scrollbar Anywhere (link) Lets you drag the page around, like with the "hand" in Adobe Acrobat.
- SmoothWheel (link) Replicates the (slow) smooth scrolling in IE. Customize it to your heart's content.
- Super Drag and Go (link) This lets you drag URLs (and other stuff like images) into a Firefox window.
- Tabbrowser Extensions (link) Adds a ton of features, like drag-and-drop, to your tabs. You can, in turn, add modules to this extension for more functionality. (This extension more-or-less works, but is mostly a legacy component from the Mozilla Suite days, and today looks excessively bloated. There's a thread that breaks down its features and how to replicate them.
- Tabbrowser Preferences (link) This is another tab browsing overhaul, which overhauls the UI for the tabs. It's pretty popular on Mozilla Update, so I guess it gets something write. Update: Reliable sources report that this one is really poorly written, leading to crap browser performance.
- Tab Killer (link) Removes tab browsing from Firefox. Some people are into this, apparently.
- Text Link (link) Lets you double-click plaintext URLs to open the associated site. Compare to Linkification, this has the advantage that it does not pass the referer onto the site you're going to, which is sometimes why people post plaintext URLs.
These are mostly complete applications built on the Firefox framework.
This is reminiscent of the old Mozilla Suite (a series of applications built on the XUL core) and is not really in keeping with the "small is beautiful" philosophy guiding Firefox development. Oh well.
- ChatZilla (link) This is the basic IRC client formerly part of the Mozilla Suite.
- FireFTP (link) A basic FTP client.
- Magpie (link) Bulk downloader for ripping whole media galleries.
- MozEdit (link) Lets you edit text if you want to.
- QuickNote (link) Lets you make sticky notes... virtually.
- RSS Editor (http://rsseditor.mozdev.org/|link) A simple RSS file editor. It's in alpha, but is still supposed to be pretty good.
- Sage (link) RSS aggregator - alerts you when your favorite site updates.
Many more are available on mozdev.org, which is a semiofficial site providing hosting focusing on applications for Mozilla and Firefox.
These provide a quick interface to the special functions on a certain website or program. A lot of communities have in-house extensions to make your life easier. For instance, if you are a socially awkward male, maybe you can download an extension to automatically buy things from camwhores' wishlists so they will take their tops off.
- Extension Uninstaller (link) Attempts to remove unwanted extensions. Because of the lack of standardization, it's unclear if this will actually work for most extensions.
- Ext2Abc (link) Alphabetic extension sorting.
- ListZilla (link) Makes a pretty list of the extensions you are currently using. This is very, very geeky.
Obviously, there are a gazillion extensions available. If you let me know what you like, the list can be even better!
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