Pre-roll ads are short video advertisements that play before the main content of a video, such as a movie or a YouTube clip. These ads typically last anywhere from 5 to 30 seconds and are designed to capture the viewer's attention before they watch their desired content. Advertisers use pre-roll ads to promote products or services, aiming to reach a wide audience. Viewers often have the option to skip the ad after a few seconds, which can influence how effective the ad is in delivering its message.