Apple has announced its OS X Mavericks update for Macs is available for free and downloadable today.

The firm made the announcement at its special event in San Francisco today. In something of a surprise the new version of the operating system, 10.9 to be exact, is a totally free upgrade for OS X users.

See also: New iPad mini 2, iPad 5 launch event: live stream, live blog of Apple's 2013 iPad launch.

Apple said it wants to make Mavericks available to as many Mac users as possible so whether you have an iMac from 2007, or a Mac mini from 2009, you're entitled to Mavericks. If you have Mountain Lion, Lion or even Snow Leopard, you can update to Mavericks in one single step.

The Cupertino company said that installing Mavericks will give some users increased battery life; up to an extra hour of web browsing and a bonus hour and a half of watching iTunes video.