User operation prohibition

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The user operation prohibition (abbreviated UOP) is a form of digital rights management used on video DVD discs. Most DVD players prohibit the viewer from performing a large majority of actions during sections of a DVD that are protected by this feature, and will display the no symbol or a message to that effect if any of these actions are attempted. It was intended for copyright notices and the ubiquitous (at least in the United States) FBI warning. Some publishers run protected commercials on their DVDs, which is widely seen as an abuse of the feature.

Some DVD players will ignore the UOP flag, allowing full control over DVD playback. Virtually all software players that use DeCSS to decrypt DVDs ignore (or rather do not implement) the flag. There are also modchip available for some standard DVD players for the same purpose, although modifying a device may be illegal in some countries. The UOP flag can be removed in DVD Decrypter, DVD Shrink, and AnyDVD.

Nevertheless, removing UOP does not always restore the functionality of the navigation in the protected parts of the DVD. This is because those parts are sometimes lacking the navigation commands which allow skipping to the menu or other parts of the DVD. This has become more common in recent titles, in order to circumvent the UOP disabling that many applications or DVD players offer.