The challenge filed Friday in a federal appeals court in New York had been expected since a June ruling rebuffed Viacom's copyright infringement lawsuit against YouTube and its owner, Google Inc.
Viacom Inc. had sought more than $1 billion in damages, alleging YouTube built its popular video site by turning a blind eye to piracy. The rampant copyright violations included material taken from various Viacom outlets, including cable channels MTV, Comedy Central and Nickelodeon.
But the judge overseeing the case concluded YouTube couldn't be held liable because it promptly removed illegal content after being notified of a violation.
Google believes the lower-court ruling will be upheld.