TikTok virality can be a mystery, but apparently, it’s not all up to chance: A Forbes investigation has revealed that staff at TikTok and ByteDance can select individual videos for broader distribution in a practice known as “heating.”

According to an internal document, “The heating feature refers to boosting videos into the For You feed through operation intervention to achieve a certain number of video views. The total video views of heated videos accounts for a large portion of the daily total video views, around 1-2%, which can have a significant impact on overall core metrics.”

TikTok and other social media platforms have been accused of shadowbanning content to suppress views in the past, but this is the first we’ve heard of human content moderation that does the opposite.

What’s the point of promoting some videos over others? Sources told Forbes that TikTok often used heating to build relationships with influencers and brands. After all, account holders may be more likely to spend more time (and money) on a platform if their videos appear particularly successful.

TikTok has defended heating, saying the practice is used to “promote some videos to help diversify the content experience and introduce celebrities and emerging creators to the TikTok community. Only a few people…have the ability to approve content for promotion in the U.S., and that content makes up approximately .002% of videos in For You feeds.”

Heating privileges at TikTok may be limited, but according to the Forbes report, employees with access to the magic virality button have even used it to promote their own content.

TikTok’s been moving towards increased transparency in recent months, especially with the introduction of the “Why This Video” info panel. The new feature, which tells users why a particular video has landed on their FYP, may even be used to explain if a video has been heated.