Facebook is reportedly set to start introducing autoplaying video ads into its Messenger platform. The ads will begin rolling out on Monday, initially appearing for a small number of users as the company carefully monitors users’ responses.

According to Quartz, the ads will automatically start playing as you scroll through your messages, but Facebook is hoping that the format will still feel unintrusive, claiming that they are rolling out video ads “gradually and thoughtfully”. Facebook is committed to treating Messenger as a different environment to the main app’s News Feed or Instagram’s native video posts.

While users will remain “in control of their experience” according to Facebook, that is unlikely to mean that Messenger users will be able to opt out of advertising entirely if the initial trial proves successful; users will likely have similar controls to those of Facebook’s main app and Instagram, where they can hide specific ads, report unsuitable ads or manage their targeting preferences.

Facebook first started selling ads within Messenger 18 months ago, but so far has stuck to static ads rather than video. The company has admitted in the past that it is running out of room for ads within the flagship Facebook app, and is increasingly looking at expanding into new areas, like the Facebook Marketplace and Messenger. Success with ads inside Messenger could also result in Facebook-owned WhatsApp finally being opened up to marketers.

Speaking to Recode from the Cannes Lions advertising festival, Stefanos Loukakos, head of Messenger business at Facebook said that user experience would remain a “top priority” for the firm, and that it had not committed fully to video ads in Messenger yet.

“However, signs until now, when we tested basic ads, didn’t show any changes with how people used the platform or how many messages they send,” said Loukakos. “Video might be a bit different, but we don’t believe so.”