When?

When are film trailers realised?

Film trailers are produced at the same time as the film but by a different team specialised in the production of trailers. They use the same footage that has been shot for the film to depict a brief narrative.

Timing the release of a trailer is important as it has to be enough time before to distribute the trailer, and generate excitement and hype, however it can't be too long before the films release as it may be forgotten. They can be released up to over a year before the film is released. 

Many films have several teaser trailers or promotional videos before there main trailer or trailers.

Here is an example of a teaser trailer released before the official trailer. Teaser trailers build excitement for the release of the official trailer.