Consumers who recently purchased Warner Brothers’ final Harry Potter film on DVD or Blu-ray found a surprise in the package: a digital copy of the movie in the new UltraViolet format. Although the name is not yet familiar, UltraViolet represents Hollywood’s first step into the cloud — the much-hyped idea that media will be stored on remote servers and accessed by various devices.

The idea behind UltraViolet is simple: The format allows buyers to own rights to films, which they can store in a “digital locker” and access via various Internet services. It’s potentially a huge convenience for consumers, who now have a dizzying number of devices (phones, tablets, computers) on which they can watch video content, and indeed, some 750,000 households in the U.S. and Britain have set up UltraViolet accounts, its backers say.

For the studios the stakes are high: DVD sales, which peaked at $15.5 billion in 2004, have stalled as consumers have turned to streaming services such as Netflix (NFLX) or, worse, illegal downloads. The studios that have announced releases in the UltraViolet format (Fox is expected to announce soon; Disney (DIS) remains a holdout) believe UltraViolet will help goose home video sales by enabling consumers to build a remotely stored library of movies. “We know consumers like collecting movies,” says Mitch Singer, president of the Digital Entertainment Content Ecosystem, the consortium that controls UltraViolet.

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