Opera has released Opera 10 today, a major update to its desktop browser featuring built-in page compression and a revamped tab bar that automatically shows thumbnails of open pages.

The free browser can be downloaded for Windows, Mac OS X and Linux in more than 40 languages from the Opera website. The browser also works in Snow Leopard, Apple's newest operating system.

Opera Turbo, the name for the browser's on-the-fly compression engine, can speed up slow connections, such as ancient dial-up or balky broadband, said the company, claiming that its tests shows an eight-fold performance improvement over rival browsers. "Opera Turbo is our newest innovation, and one we think everyone should try, because we all will face a slow connection at some point," said Jon von Tetzchner, Opera's CEO.

At the top of the visible change chart is a retooled tab bar, which can be resized with a click and drag. More importantly, Opera displays thumbnails of each tab's contents. Users can also move the tab bar to the side of the browser window -- ideal for wide-screen monitors -- rather than leave it at the default top position.

One of the most notable missing pieces in the update is Opera Unite , a technology platform introduced in mid-June that adds a compact web server to Opera and lets users share files, photos and music without using third-party peer-to-peer services. Opera Unite was criticised over security concerns and remains in the company's labs, and although it requires Opera 10, it has not yet been baked into the browser.

Opera did not immediately respond to questions about Opera Unite's timetable.

The browser has an uphill battle convincing users to switch, even with the features launching in version 10. Overall, Opera currently accounts for just 2.1 percent of the global browser market, according to web metrics company Net Applications. (Irish measurement firm StatCounter measured Opera's August share somewhat higher, at 2.7 percent.)

That puts Opera in the No. 5 spot, behind Mozilla's Firefox, Apple's Safari and Google 's Chrome, all of which trail Microsoft 's Internet Explorer (IE) by large margins.  In fact, Opera has been in the news more often this year for its part in the European Union's (EU) anti-trust case against Microsoft than for any technology move it's made.