A teaser trailer, or just teaser, is a short trailer used to advertise an upcoming film, television program, video game, or product.
Teasers, unlike typical theatrical trailers, are usually very short in length (between 30–60 seconds) and usually contain little, if any, actual footage from the film. Sometimes, it is merely a truncated version of a theoretical trailer. They are usually released long in advance of the film they advertise. One of the reasons for the name "teaser" is because they are shown usually a long time (one or one and a half years) before the movie comes out, so as to "tease" the audience.
Teasers are also commonly used in advertising.