In Amazon's case, the e-commerce giant used vendors' sales figures to decide which items it should sell and how much to price products to get an edge over everyone else, the CMA said.

The internet giant promoted its products with its Buy Box feature, and it further cut into retailers' margins by charging extra costs if they wanted to use Amazon's Prime delivery services, the CMA said.

Now, Amazon has committed to doing less of that sort of thing.

The CMA has stated that Amazon will be prevented from using third-party seller data that gives it an unfair commercial advantage. Rivals will be allowed to negotiate rates with independent delivery contractors working on behalf of Amazon.

The Buy Box will also better support merchants’ items instead of Amazon-led products or those from sellers that have bought into the company’s packing and delivery services.

Meanwhile Facebook rivals don’t have to share their data with the social notworking site.

"Going forward, competitors of Facebook Marketplace that advertise on Meta platforms can 'opt-out' of their data being used to improve Facebook Marketplace," the CMA said.

Brits make Amazon and Facebook sign data pledge.

Can’t sell it to give them an unfair advantage

The UK’s Competition and Markets Authority has made Facebook and Amazon promise not to sell third-party seller data that gives it an unfair commercial advantage.

In Amazon's case, the e-commerce giant used vendors' sales figures to decide which items it should sell and how much to price products to get an edge over everyone else, the CMA said.

The internet giant promoted its products with its Buy Box feature, and it further cut into retailers' margins by charging extra costs if they wanted to use Amazon's Prime delivery services, the CMA said.

Now, Amazon has committed to doing less of that sort of thing.

The CMA has stated that Amazon will be prevented from using third-party seller data that gives it an unfair commercial advantage. Rivals will be allowed to negotiate rates with independent delivery contractors working on behalf of Amazon.

The Buy Box will also better support merchants’ items instead of Amazon-led products or those from sellers that have bought into the company’s packing and delivery services.

Meanwhile Facebook rivals don’t have to share their data with the social notworking site.

"Going forward, competitors of Facebook Marketplace that advertise on Meta platforms can 'opt-out' of their data being used to improve Facebook Marketplace," the CMA said.