Editors' note: Updated June 30, 2009, at 5:55 p.m. with more extensions details.
Updated at 12:42 p.m. with more add-on details and a statement about Google Gears.

Firefox 3.5 logo

Like you, we've been hotly anticipating the launch of Firefox 3.5 for Windows and Mac. Yet every time a browser receives a major update, it ghosts out a good chunk of those favorite, ingenious, and time-saving extensions we've come to rely on. That is, until the lagging publishers update their add-ons to make them compatible once again.

Google is one high-profile example with Gears. "We're working on pushing out a new Gears version that support FF 3.5," Google's Aaron Boodman wrote to Gears users Monday online. "We typically wait until the official 'gold' release of Firefox is pushed, because otherwise, we keep having to do new builds every time a new RC is pushed."

We've compiled what is by no means an exhaustive list of extensions that we find do and do not work in Firefox 3.5 at launch. Add your insights to the comments--we'll be updating this post throughout the day. Mozilla also has a compatibility report that takes the 95 percent most-used add-ons and matches them to their version numbers. A quick glance will tell you if your favorites are a go.

If you want to attempt to force Firefox to accept old add-ons, there are ways, but prepare yourself for consequences: bugs, stability breakdowns, and tampering with advanced settings. Two Firefox 3.5-ready add-ons that often correct incompatibility are Nightly Tester Tools and MR Tech Toolkit. CNET Executive Editor Tom Merritt shows you another way to teach the new 'Fox old tricks. Both methods essentially override the maximum version number rule that keeps Firefox from loading an add-on that's been approved for a previous version build, like 3.0. Nightly Tester Tools, for instance, is cleared for versions 3.0b5 through 3.6a1pre.

Works with Firefox 3.5:
Adblock Plus
All-In-One Sidebar
AVG Safe Search
CoolIris (requires manual redownload or reinstallation)
Customize Google
Forecastfox Enhanced
Google Preview
Google Toolbar
IE Tab
Java QuickStarter
McAfee Site Advisor
Personal Menu
Read It Later
Roboform (PC only--requires manual redownload or reinstallation)
Select-n-Go by Cleeki
Session Manager
Site Launcher

Doesn't work with Firefox 3.5:
Better Gmail 2
Drag & DropZones
Google Gears (read above)
Minimize To Tray Enhancer
Open in Google Chrome
Tab Mix Plus
Tab Minus

Update Notifier

Note: Windows links for Firefox add-ons should also work on Macs.

Jessica Dolcourt reviews smartphones and cell phones, covers handset news, and pens the monthly column Smartphones Unlocked. A senior editor, she started at CNET in 2006 and spent four years reviewing mobile and desktop software before taking on devices.