In the context of American jurisprudence, a facial challenge is a manner of challenging a statute in court, in which the plaintiff alleges that the statute is always, and under all circumstances, unconstitutional, and therefore void. It is contrasted with an as-applied challenge, which alleges that the statute may be, in part, unconstitutional, in redress of specific and particular injury.

A facial challenge to a legislative Act is, of course, the most difficult challenge to mount successfully, since the challenger must establish that no set of circumstances exists under which the Act would be valid." United States v. Salerno, 481 U.S. 739, 745 (1987)
If a facial challenge is successful, a court will declare the statute in question facially invalid, which has the effect of striking it down entirely. This contrasts with a successful as-applied challenge, which will result in a court narrowing the circumstances in which the statute may constitutionally be applied without striking it down. In some cases—e.g. Gonzales v. Carhart or Crawford v. Marion County Election Board, a facial challenge has been rejected with either the court or concurring Justices intimating that the upheld statute might be vulnerable to an as-applied challenge.
In First Amendment cases, another type of facial challenge is enunciated in the overbreadth doctrine. If a statute reaches to include substantial protected conduct and speech in relation to the legitimate reach of the statute, then it is overbroad and thus void on its face.
this term could be useful in the marketing of videos by people that are being prosecuted for obscenity.