Since mobile devices are held vertically most of the time, most mobile users prefer not to have to turn their phone on the side to view an ad or video if they don’t have to. Due to this fact, the vertical video demand has grown has grown and could give horizontal video ads a run for their money.

This may come as a shock to some. After all, not long ago, anyone who shot a video holding their phone vertically was criticized for not having their phone turned the right way. This is because when these videos are uploaded online, they’re accompanied by two large black rectangles on either side. However, attitudes are changing and Apple’s Face Time video chat technology has helped to normalize the vertical video idea.

Furthermore, the simple truth of the matter is that holding the phone in its vertical position is more natural and comfortable for users when viewing or shooting a video. As such, it only makes sense that vertical videos would inevitably become a trend.

In fact, an estimated 98% of mobile users read with their phone in a vertical position. What’s more, according to previous claims from the popular instant messaging and multimedia mobile app Snapchat, vertical video ads have nine times as many completed views compared to horizontal video ads. Additionally, Facebook’s new release of larger vertical video has resulted in much larger sized video previews in the News Feed. Now, a single video takes up most of the screen and keeps other items in the News Feed out of sight.

Still, in spite of these facts, there is a fight for domination between vertical and horizontal video in regard to mobile ads.

Why the battle? While Snapchat, Instagram Stories, Facebook and other apps have figured out how to make vertical videos work, most brands are slow to adopt this form of video because they prefer to stick with what they know. Moreover, many companies are still trying to figure out the best way to shoot a vertical video, especially with traditional camera equipment. Technical problems need to be overcome and creative designers need to rethink how they frame and create shots.

Yet, in spite of these difficulties, the increasing number of users spending time viewing videos in vertical mode (e.g. 5% in 2010 vs. 29% in 2015), means that companies will need to find a way to adapt if they want to reach their audience and remain relevant.