Napster's battle with the recording industry over the future of music distribution reaches a climax later today.

The decision to either close Napster or allow it to continue will be taken by the Ninth US Circuit Court of Appeals in San Francisco. The outcome will affect millions of regular Napster users, who download music using the service. A decision in favour of the record labels could bring that activity to a halt.

Over the weekend, nearly 10,000 users flocked to the service - sharing two million songs - fearing that today would be Napster's last.

The ruling from the three-judge panel will determine who will control music distribution, by clarifying copyright law in the digital age.

The recording industry first sued Napster in December 1999, contending it violates the copyrights of record labels.

Plaintiffs including BMG, Universal, Warner, EMI and Sony are requesting monetary damages and a permanent injunction preventing copyrighted songs being swapped over Napster's service.

Napster is the brainchild of Shawn Fanning, a 20-year old programmer who dropped out of Northeastern University in early 1999 to build a system that would allow him and his friends to trade music online.

Napster catalogues songs available on the hard drives of users, making them easy to find. The service then establishes a connection between two users, so they can swap songs over the Net. Napster capitalizes on the popularity of MP3, a digital music format that provides the crispness of a CD, but at about a third the size.

With little marketing and a shoestring budget, Napster took the world by storm. It says it has 57 million subscribers, although some users are believed to have registered multiple times.

Napster has threatened to turn the decades-old recording industry on its head by introducing a new way for musicians to bypass labels in distributing their music. The service has been the focus of global debate, drawing strong words from Congress, and senior executives in the Internet and recording industries.