The Xbox maker has thrown its backing behind Epic Games, which makes Fortnite, as it continues to publicly fight with Apple over its App Store rules.
Apple and Epic have come into conflict because of rules that require any app or game sold through the App Store to pay a cut of its revenue to Apple, as part of the rules of its platform.
Epic has refused to follow that rule, adding a new payment system that allowed it to get around the App Store rules, and suing both Apple and Google.
The dispute led not only to Fortnite being thrown out of the App Store, but a threat from Apple that Epic could be cut off from Apple's development tools entirely. That would cover not only Fortnite but also the variety of games that require Epic's software – not only its own titles, such as Fortnite, but a variety of third-party ones too.
In response to that threat, Epic began separate legal proceedings with the hope of securing an injunction that would stop Apple from carrying out on that threat.
Now Xbox, part of Microsoft, has thrown its support behind Epic's request, filing a statement with a court in California that gave backing to the demand that it keeps access to its development tools.
Epic losing access to Apple's development tools would impact other software beyond Fortnite, including its Unreal Engine gaming software, which is used by many other game developers, including Microsoft, to build their own products on.
"Today we filed a statement in support of Epic's request to keep access to the Apple SDK for its Unreal Engine", Xbox boss Phil Spencer said in a tweet.
"Ensuring that Epic has access to the latest Apple technology is the right thing for gamer developers & gamers."
In the statement, filed to a US district court in California, Microsoft's general manager for gaming developer experiences, Kevin Gammill, said: "Epic Games' Unreal Engine is critical technology for numerous game creators including Microsoft."
He added that many other, smaller developers can not afford to build their own gaming engines, so are reliant on third-party software such as the Unreal Engine.
"As a result, Epic's Unreal Engine is one of the most popular third-party game engines available to game creators, and in Microsoft's view there are very few other options available for creators to license with as many features and as much functionality as Unreal Engine across multiple platforms, including iOS," Mr Gammill said.
"Denying Epic access to Apple's SDK and other development tools will prevent Epic from supporting Unreal Engine on iOS and macOS, and will place Unreal Engine and those game creators that have built, are building, and may build games on it at a substantial disadvantage.
"Because iOS is a large and growing market for games, Apple's discontinuation of Unreal Engine's ability to support iOS will be a material disadvantage for the Unreal Engine in future decisions by Microsoft and other game creators as to the choice of an engine for new games.
"Apple's discontinuation of Epic's ability to develop and support Unreal Engine for iOS or macOS will harm game creators and gamers."
The dispute between Apple and Epic began when a payment option was added to Fortnite which allowed users to pay for in-game items directly through Epic.
According to the rules of both Apple and Google's app store, purchases made for digital items within an app must be done through Apple or Google's respective payment system, from which the companies then take a cut of up to 30%.
Both Apple and Google then removed Fortnite from their app stores, although mobile users on Google's Android can still download the app directly from Epic's website.
The incident reignited debate around app store payment systems, which some developers have previously called unfair and anti-competitive.
Apple has said Epic created the problem "for itself" but that it could "easily be remedied" if it updated Fortnite to "comply with the guidelines they agreed to and which apply to all developers".
"The App Store is designed to be a safe and trusted place for users and a great business opportunity for all developers," the iPhone maker said.
"We won't make an exception for Epic because we don't think it's right to put their business interests ahead of the guidelines that protect our customers."
Additional reporting by agencies
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