Microsoft says Apple’s App Store rules are to blame for the continued delay of the Xbox mobile app store it announced last summer. In an amicus brief filed this week first spotted by The Verge, Microsoft expressed support for Epic Games in the company’s long-running bout against Apple. The company also expressed concern that Apple could succeed in overturning the injunction that has opened the floodgates for payments outside of apps that circumvent Apple’s 30 percent fee.

“Among its other provisions, the order challenged in this appeal would prevent Apple from requiring consumers and app developers (like Microsoft) to use Apple’s in-app payment processing system as the exclusive means for the purchase of digital goods or services for use within iOS apps available for download on the Apple App Store, Microsoft said in the brief. “In part as a response to the district court’s injunction issued over a year ago, Microsoft undertook significant work to prepare new consumer offerings. However, Apple’s evasion of the injunction has hampered Microsoft in delivering these offerings.”

The offering in questions would have allowed Microsoft to direct users of its apps like the Xbox app or games like Candy Crush and Minecraft to “separate platforms for payment.” That’s exactly what Spotify and Amazon’s Kindle app has started doing in recent weeks, letting those companies avoid Apple’s standard in-app purchase fees.

“The district court’s injunction allows Apple to maintain its in-app exclusivity but at least should have enabled Microsoft to offer consumers a workable solution by launching its own online store — accessible via link-out — for in-app items to be purchased off-app and used in games or other apps,” the brief reads in part. “And that is what Microsoft wants to do. But even this solution has been stymied by Apple.”

Apple filed an appeal against the injunction earlier this month, and just a few days later it asked the Ninth Circuit to halt enforcement of the original ruling while it works through its appeal. Microsoft, for its part, is urging the court to enforce the injunction while the courts handle the appeal. The company points out that Apple itself has said that the policy changes it made in response to the injunction “can be undone,” raising concern that without firm enforcement by the courts, Apple could pull the rug at any given moment.

While things are moving quickly, with apps like Fortnite already returning to the App Store in the US, Microsoft remains in a holding pattern awaiting a firm outcome in the case. It seems they want to avoid a situation where the Xbox mobile store is released, only to be taken down should Apple win on appeal.

Update, May 21, 2025, 3:42PM ET: This story has been updated with a link to the amicus brief that Microsoft filed and now includes more details from that filing.