Video blogs must make clear when their content is advertising, Britain's ad standards body announced as it released new guidance for vloggers on Wednesday.
Any advertisements in video blogs, which are increasingly popular and influential with teenagers, must be "obviously identifiable", the Committees of Advertising Practice said.
It issued an eight-point guide explaining when videos should carry labels such as "advertisement feature" on the screen, or in the title of the video.
"Wherever ads appear we should be confident we can trust what an advertiser says; it's simply not fair if we're being advertised to and are not made aware of that fact," said CAP director Shahriar Coupal.
"Our guidance will give vloggers greater confidence that they're sticking to the rules which in turn will help maintain the relationship and trust they've built with their followers."
The rules come after Britain's ad watchdog, the Advertising Standards Authority banned several YouTube videos by popular vloggers praising Oreo biscuits, saying they were not clearly labelled as adverts.
The new advice covers a variety of scenarios, including where a brand sponsors a vlogger to create a video, product placement within a vlog, or a vlogger is promoting their own products.
For the latest tech news and reviews, follow Gadgets 360 on X, Facebook, WhatsApp, Threads and Google News. For the latest videos on gadgets and tech, subscribe to our YouTube channel. If you want to know everything about top influencers, follow our in-house Who'sThat360 on Instagram and YouTube.