More than a dozen celebrities in the UK have agreed to make it clearer when they are being paid or rewarded to post on social media.
The UK's Competition and Markets Authority (CMA) has announced that 16 prominent online 'influencers' will flag when they have been been paid, or if they've received any gifts or loans of products they endorse.
The celebrities include singers Ellie Goulding and Rita Ora, actress Michelle Keegan and models Alexa Chung and Rosie Huntington-Whiteley.
Bloggers, vloggers and reality TV stars are among the others who've agreed to change their social media practices.
The CMA has stressed it has not made a finding on whether the influencers' practices breached UK consumer law.
The watchdog said it has also sent warning letters to a number of other celebrities, "urging them to review their practices".
In a statement, Andrea Coscelli - chief executive of the CMA - said: "Influencers can have a huge impact on what their fans decide to buy. People could, quite rightly, feel misled if what they thought was a recommendation from someone they admired turns out to be a marketing ploy.
"The enforcement action taken by the CMA has seen a number of social media stars pledge to be more transparent when posting online. It also sends a clear message to all influencers, brands and businesses that they must be open and clear with their followers."