What’s the magic video length to attract smartphone users? According to Instagram founder and current chief executive Kevin Systrom, it’s 15 seconds. That’s the maximum length chosen for Instagram’s new video feature, announced yesterday. The popular Facebook app, which was originally designed as a photo-sharing service and now boasts 130 million users, now includes a user-friendly feature for sharing video clips as long as 15 seconds—more than twice the length of Twitter’s popular Vine video-sharing service.

Why 15 seconds? Systrom says the number was arbitrarily chosen because six seconds would limit users’ creativity and longer videos could overload smartphones’ processors or simply take too long to load. Furthermore, 15 seconds should appeal to advertisers since they are already accustomed to buying 15-second television ads. Although Systrom claims Instagram has no immediate plans to sell advertisements, it’s obviously only a matter of time before users start noticing ads within the app.

“Over time, we’ll figure out how advertising ends up being OK on Instagram in a useful way,” Systrom said during a news conference announcing the new feature.

Although Vine videos are typically too short to sell ads, there is precedence in the market for adding commercials to shared videos. Google, in fact, has been quite successful in streaming ads right alongside posted YouTube videos. And as services such as Vine, Keek and Socialcam have grown in popularity among younger users, it was only a matter of time before Facebook threw its hat into the newly-emerged ring, particularly after it spent $1 billion to purchase Instagram in April 2012.

“We want to create meaningful ways to help you discover new and interesting accounts and content while building a self-sustaining business at the same time,” Systrom said.

So how does it work? During the launch event held at Facebook’s California headquarters, Systrom explained that in video mode users can tap their phones to start and stop recordings, much like they do when using Vine. Instagram video will also allow users to delete portions of videos already recorded, a benefit Vine doesn’t offer. In another departure from Vine’s technology, Instagram will also include its 13 signature filters designed just for videos.

Hate how shaky your videos end up when you can’t hold your hand still? Instagram has the answer: Cinema, its stabilization feature, creates steadier videos from shaky shots.

Instagram’s video feature is now available through an app update.