• by Erik Sass , Staff Writer, November 12, 2015

The addition of subtitles to long form video in Facebook’s Newsfeed boosted viewer engagement and completion rates substantially, according to a new study by Adaptly and online publisher Refinery29, which tested subtitles, pre-roll trailers previewing the video, and various combinations of these. For the purposes of the study Adaptly and Refinery29 defined long form video as any video content over two minutes in length.

Adaptly compared the results for the same piece of video content in four different configurations and found that the addition of subtitles increased the completion rate from 6.84% to 7.09%, and also increased the rate of social sharing, liking and commenting on the videos (measures of engagement). The share rate increased from 0.23% to 0.29%, the like rate from 1.06% to 1.17%, and the comment rate from 0.07% to 0.09%.

The increased engagement and completion reflects the fact that Facebook doesn’t automatically turn on audio for video content; subtitles allow the consumer to engage with the content despite that.

By contrast, the addition of a pre-roll trailer previewing the video increased the likelihood that the viewer would watch at least three seconds of the video itself, but decreased the actual completion rate.

Putting it all together, trailers without subtitles earned the lowest completion and engagement rate, 0.10%, while subtitles alone (without a trailer) had a completion rate of 0.39% -- an almost four-fold increase.

It’s worth noting that some of the content tested was quite a bit longer than two minutes. Adaptly president Sean O’Neal noted: “We are seeing a lot of data to indicate that the Facebook audience will engage with longer-form, custom content from brands when it is well-produced, and entertaining or informative. In the case of this study, this audience was viewing and completing a seven minute branded video on their mobile devices.”