Meta, Microsoft, X and online dating giant Match Group hit at Apple on Wednesday for overcharging on app purchases.

The four companies filed a rare joint amicus brief in a California court in charge of applying a ruling that Apple must allow companies to link to alternative payment options outside the app store for iPhone users.

That ruling was stemmed from a 2020 lawsuit by video gaming giant Epic Games, which has been fighting Apple in courts across the globe for years over its strict app store policies.

Apple takes a cut of as much as 30 percent on all financial transactions in its app shop, prompting complaints about an unfair "tax" on companies.

A federal court in San Francisco overwhelmingly rejected Epic's lawsuit in 2021, offering only a concession that apps could indicate other ways of paying for services outside of Apple's ecosystem.

But Apple's compliance with the order earlier this year drew a furious response from Epic, which went to court arguing that it was defying the judge's intentions.

Apple's proposed solution allows it a 12 to 27 percent fee on external purchases outside its app store, which amounts to just a small discount from what it charged within the app store.

"The Apple Plan comports with neither the letter nor the spirit of this Court's mandate," Meta, Microsoft, X and Match said in their joint filing on Wednesday, in support of Epic.

The plan's "new restrictions are plainly designed to render alternatives to Apple's in-app purchases impractical for developers, and inaccessible and unappealing to consumers," they added.

Apple told AFP that it has "fully complied with the injunction," of the judge, which allows it to take measures needed to protect users.

These measures also "guard against the uncompensated use of, among other things, Apple's platform, services... and proprietary tools and technologies protected by intellectual property," the company said, quoting its compliance statement sent to the court.