Originally Posted by PR_Phil

yes, they do, for television and in theater, which is their medium. they can be longer on the internet and often are.

"The Motion Picture Association of America (MPAA) mandates that theatrical trailers not exceed 2 minutes and 30 seconds in length, and each major studio is given one exception to this rule per year."

if you are watching trailers on the internet, and they are around 90 seconds, they were shot for television (in most cases) if they are around 2:20 - 2:30 they were shot for viewing in the theater (theatrical trailers); if their length is longer than 2:30, they were specifically shot for internet promotion.