The iPhone maker may have to allow competitors to operate their own app stores on Apple devices in the UK, after a decision from the market watchdog.
This represents a significant change to Apple's well-known "closed system" where applications can only be installed from its own App Store.
But the UK competition watchdog has classified both Apple and Google as having "dominant market position" - indicating they have significant control over mobile platforms.
The CMA said the two companies "could be restricting innovation and market rivalry".
But the regulator emphasized it did not "determine or presume misconduct" from the companies.
"Mobile applications generates one and a half percent of the British economy and supports around four hundred thousand positions, which is why it's essential these sectors function properly for enterprises," stated a top executive from the CMA.
Approximately 90-100% of UK mobile devices run on Apple or Google's mobile platforms, creating what the regulator calls an "effective duopoly".
Based on recent analysis, 48.5% of British smartphone users use an Apple device - which runs Apple's iOS - with the vast majority of the rest using Google's Android.
The CMA's investigation focused on how dominant Apple and Google's own apps are versus competitors - as well as their browsers and platform software.
It is unclear what changes the regulator will look to request, but previously it published guidelines outlining potential measures it could take.
These include mandating it to be more straightforward for people to transition between Apple and Android devices, and for both firms to list applications "in a fair, objective and transparent manner" in their marketplaces.
Apple specifically may be compelled to allow alternative app stores on its devices, and enable people to install apps straight from developer sites.
This would follow a similar ruling in the EU, which previously took action against Apple for anti-competitive behaviour.
Apple warned the UK could lose access to getting new features - as has happened in the EU - which the organization blames on strict rules.
For example, some AI capabilities which have been rolled out in other regions are not accessible in the European market.
"Apple encounters fierce competition in every market where we do business, and we work tirelessly to create the finest offerings, solutions and customer interface," the organization said in a statement.
"Britain's implementation of EU-style rules would weaken that, resulting in consumers with reduced data protection and security, slower availability to latest functions, and a divided, less seamless user journey."
Google device owners can presently use third-party app stores - though commentators say they are not as user-friendly as the company's official application marketplace.
The CMA's roadmap said the search company may have to "modify the interface" of installing applications directly from online sources, as well as "eliminate barriers" when using third-party platforms.
"There appears to be no the rationale for the current classification," a Google policy executive remarked.
The executive said "the majority" of Android users use third-party platforms or install applications directly from a developer's website, and claimed there is a far greater range of applications offered for Android users versus those on iOS products.
"Currently available are twenty-four thousand Google-compatible devices from thirteen hundred phone manufacturers globally, facing intense competition from Apple's platform in the UK," the spokesperson continued.
Android is an freely available software, which means developers can use and build on top of it for no cost.
The company contends this means it opens up market competition.
But consumer groups said curbs on these firms' dominance in other countries "are already helping businesses to develop and giving customers more choice".
"Their dominance is now creating genuine problems by restricting choice for users and competition for businesses," stated a consumer advocate.