Google just pushed an update to the stable channel of Chrome on Windows, bringing support for extensions and bookmark syncing to everyone who isn’t living on the bleeding edge of Chrome.

The major features in this release (officially labeled 4.0.249.78—uh, we’ll just call it 4.0):

• Extensions
• Bookmark sync
• Enhanced developer tools
• HTML5: Notifications, Web Database, Local Storage, WebSockets, Ruby support
• v8 performance improvements
• Skia performance improvements
• Full ACID3 pass, due to re-enabled remote font support (with added defense against bugs in operating system font libraries)
• HTTP byte range support
• New security feature: “Strict Transport Security” support
• Experimental new anti-reflected-XSS feature called “XSS Auditor”

They’ve also pushed out a handful of security fixes, listed on the Chrome Releases blog post. Google’s spinning this release as adding “over 1,500 new features” to Chrome by virtue of the number of extensions already available to the Chrome community. This update isn’t the final blow to Firefox or anything along those lines, but we can’t help but think the folks at Mozilla would be a little worried.

Extensions are a large part of what’s set Firefox apart from Chrome, while Chrome has often out-paced Firefox in arenas like performance. As Chrome extensions hit the mainstream stable release, we could see a lot of people considering the switch.

Chrome 4.0.etc. is a free, stable release for Windows only but you can only expect the other OS’s versions to be caught up fairly quickly.