California federal court judge Yvonne Gonzalez Rogers on Friday ordered Apple to loosen control over its App store payment system, in a blow for the tech giant.

Rogers ruled in the antitrust battle between Apple and Fortnite maker Epic Games, saying that Apple could not prohibit developers from adding buttons or links in their apps that direct users to other payment options outside of Apple's own in-app purchase apparatus.

The change, which has a significant potential to alter the digital economy, was strongly demanded by app developers due to the commission of up to 30% on purchases that Apple charges.

The order also said that Apple could not prohibit developers from communicating with customers using contact details that the app producers obtained when they signed up within the app.

However, there was some consolation for Apple, as the judge also ruled that Epic had not proved its claim of illegal monopoly against the tech giant.

"Apple enjoys considerable market share of over 55% and extraordinarily high profit margins... (but) Success is not illegal," Rogers said.

"Epic Games failed in its burden to demonstrate Apple is an illegal monopolist," she added.

Rogers granted a preliminary injunction sought by Epic, but also directed the game maker to pay Apple $4 million in damages.

"We consider this a huge win for Apple," said the iPhone maker.

Epic said that the order was essentially a loss for app producers who rely on the App Store in the multi-billion-dollar mobile gaming industry, and for consumers.

"We will fight on," Epic CEO Tim Sweeney said in a tweet, while a company spokesperson later told the media that they would appeal.

dvv/rc (AFP,dpa)