Snapchat, the popular social image sharing app, recently ran the first ad on their platform since its inception. If Universal Pictures, the movie studio who bought the ad, is to be believed, the results are already showing the advertising exercise was a great success.

It is hard to tell how the format will work for smaller brands, but Universal vice president of digital marketing Doug Neil said “millions” of viewers have seen the 20-second trailer for the horror movie “Ouija”.

However there has been some fallout from the ad tests, especially on Twitter. Some users were surprised by the ads or confused by their disappearance after playing. For big marketing ventures like “Ouija” this isn’t much of a problem, especially as the platform perfectly attracts their demographic, but it could be an issue with more niche or localized brands if Snapchat ever expands the ad platform.

Snapchat’s ad medium does offer one unique benefit from the plethora of other monetizing social media platforms. While Facebook’s videos autoplay for anyone who happens to scroll by, Snapchat’s ads have an incredibly wide reach while only playing for those who actively engage the ads. While a huge range of people were shown the ad’s presence, only those who wanted to view it actually watched.

“It was a lean-in experience,” Neil said. “The people who watched the ad were ones that pressed to play so they were focused on actually viewing the content. As it turns out there were a number of people who screen captured it and it’s actually moved beyond the Snapchat window. But our goal was to get exposure in Snapchat and that was accomplished.”