Apple and Google's dominance over cloud gaming and mobile browsers will be investigated by the UK's competition regulator, it has announced.
Last year, a "market study" by the Competition and Markets Authority (CMA) concluded they had a "stranglehold" over operating systems, app stores and web browsers on mobile devices.
If the 18-month investigation finds an adverse effect on competition, the CMA can impose changes.
Both companies deny the accusations.
CMA interim chief executive Sarah Cardell said it wanted to ensure UK:
consumers received the best new mobile data services developers could invest in innovative new apps "Many UK businesses and web developers tell us they feel that they are being held back by restrictions set by Apple and Google," she added.
In the UK, the CMA says:
- 800,000 people use cloud gaming services
- 97% of mobile web browsing last year was on browsers powered by Apple or Google's software Google said its Android operating system offered a greater choice of apps and app stores than any other mobile platform. It enabled developers "to choose the browser engine they want and has been the launchpad for millions of apps".
Apple said it "believes in vibrant and competitive markets where innovation can thrive".
Its App Store had helped millions of developers turn their ideas into apps, which had supported hundreds of thousands of jobs in the UK alone, it said.
"We will continue to engage constructively with the Competition and Markets Authority to explain how our approach promotes competition and choice, while ensuring consumers' privacy and security are always protected," Apple added.