Nvidia has developed a version of its GeForce cloud gaming service that runs in the mobile web browser Safari.
Apple will not get a cut of virtual items sold within the battle royale fighting title when played this way.
Apple is embroiled in a legal fight with Fortnite's developer Epic, which led the iPhone-maker to remove the game from its iOS App Store.
Epic has claimed that the 30% commission Apple charges on in-app gaming purchases is anti-competitive.
But Apple has accused Epic of wanting a "free ride".
The case is due to go to trial in May and could take years to be resolved.
Papers filed in the case indicate that Fortnite had 116 million users on iOS, 73 million of whom only played it via Apple's operating system.
Unlike Android, Apple does not allow games or other apps to be loaded on to its phones or tablets via app stores other than its own.
But it does not restrict which third-party services can run within Safari or other web browsers available via its store.