Facebook launches auto-play video ads on news feeds
Facebook is rolling out video advertisements, beginning with a series of ads for forthcoming film Divergent.
The ads will play automatically on some news feeds although sound will only be activated if users click on them, it said on its Facebook for business page.
Ads on mobile devices will have been downloaded in advance when the device was connected to wi-fi, the firm said.
Experts said that such ads may alienate users.
"It sounds as if they are doing it in a reasonably sensitive way but if they get this stuff wrong people may stop being active and posting new content," said Alys Woodward, an analyst with research firm IDC.
"The question is do they have rich enough analytics to target ads correctly? It isn't just about an ad for a film. I care about being sent the correct movie so try and sell me the right thing," she added.Mobile users
Rumours that Facebook would introduce video ads have been swirling around for months.
Since September it has been testing ways of watching self-play videos on the social network and stressed that this extension to adverts is currently a limited trial.
"This format isn't intended for every video ad or page post video on Facebook... We'll continue to refine this new way for brands to tell stories on Facebook to ensure the best experience for people and marketers," it said.
Originally the video ads were due to start in the summer but founder Mark Zuckerberg delayed their introduction partly because of fears of how such adverts would go down with users.
Mobile users have complained that such ads would eat up their mobile data allowances.
To placate its mobile audience, Facebook has stressed that only videos that have been downloaded in advance via wi-fi will play.
"This content will not consume data plans, even if you're not connected to wi-fi at the time of playback," it said.
It added that users who do not want to watch adverts can "simply scroll past and the video will stop playing".
It is not known how much Facebook will charge advertisers for the service although in August, bank Morgan Stanley predicted it could rake in approximately $1bn (£613m) for video ads in 2014.
Its report went on to suggest that such ads could generate as much as $6.5bn by 2020.