Apple announced new chips for its Macs, which the company said Monday would make the computers more power efficient. But some worried about a different kind of power: the kind Apple wields over its developers.

Apple is switching from Intel processors, which it has used for more than a decade, to custom-designed chips made by Arm, a British company owned by the Japanese conglomerate Softbank.

The change, which Apple announced at its WWDC developer event, is no small thing. Software written for today’s Mac computers will no longer work unless it’s adapted for the new language. Apple said the change will take two years to complete.

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Apple said its “Apple Silicon” will make it easier for developers to write apps for the entire “ecosystem.” Onstage during the virtual event, Craig Federighi, Apple’s senior vice president of software engineering, said, “Users will want their favorite apps to take full advantage of the capabilities of our custom silicon.”

By switching from Intel to Arm, Apple gets to develop its own customized microprocessor. Those tailor-made chips have allowed Apple to get more processing power with less heat and battery consumption out of its iPhones, iPads and watches. Apple also incorporates more built-in security protections that make it more difficult for hackers to break into a computer.

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But transitions to new processors often create major waves for software developers. Some developers are concerned that chaos will mean opportunity for Apple, which for years has been making efforts to get developers on the Mac to distribute their products through the Mac App Store. Apple gets a hefty cut of all revenue generated through the App Store and imposes strict limitations on what the software is allowed to do.

“I can guarantee you that the fact that any developer can host their own Mac software bugs Apple terribly,” said Jason Fried, CEO of Basecamp, which has been battling with Apple over its email app developed for iPhones called “Hey.” Apple recently blocked Hey from being updated on iOS because it offered subscriptions outside of Apple’s payment system, thus avoiding Apple’s 30% cut on subscription revenue.

An Apple spokeswoman did not immediately respond to a request for comment.

Mac users have long been accustomed to downloading software directly from developer websites. By contrast, the iPhone has never allowed that level of freedom. Apps in iOS have to be downloaded through the App Store.

With the same processor base across its devices, Apple seems to be moving in the direction of iOS, where things are more tightly controlled by Apple, said Patrick Wardle, a long time developer of Mac software and principal security researcher for Minneapolis-based software maker Jamf.

“It does kind of just unify their computing platform and does make the transition for this more lockdown model easier to comprehend on Mac,” he said. “Unfortunately, we’re just moving down this path where Apple has complete control.”

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Apple’s iPad apps already work on Arm processors. Apple last year began offering a service to make iPad apps work on desktop, called Mac Catalyst. With Arm processors, that interoperability becomes even more seamless, and could help increase the number of apps downloaded from the comparatively small Mac App Store.

“If Apple decides to lock the Mac down further and require all apps to go through the App Store, it’s going to be a bitter pill,” said Matt Ronge, CEO of Astro HQ, maker of AstroPad, a drawing app that competes with Apple’s version. “I think many developers will start to seriously look at other platforms if the Mac is that locked down.”

Apple already includes an Arm-based processor inside Macs, called the T2 Security Chip, to handle some security operations. Some have described it as a mini Apple Watch sitting inside a computer.

Ben Volach, co-founder of Blix, another maker of email software, said he’s concerned that Apple will make it easier for Mac developers to transition their software to Arm processors if they distribute through the App Store, disadvantaging developers who rely on customers directly downloading software.

Apple already offers developers on the Mac App store some conveniences that aren’t available to those who don’t use the store. For instance, developers who distribute through the store automatically get “notarized,” which confirms the identity of a developer and allows the software to be installed. Developers must obtain certificates manually if they don’t go through the store. Earlier this year, Apple tightened restrictions on apps that aren’t notarized by Apple.

Apple can “make the user experience worse for running apps distributed outside the Mac App Store, with extra warnings when you first open them,” said Manton Reece, the founder of Micro.blog, a blogging platform and social network with an iOS and Mac app.

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Reining in the software free-for-all on Macs could take years, in part because Apple might invite a backlash from users and developers.

“The fact is the Mac has existed for 30 years without the App Store. It’s a whole lot harder to cram that back into the App Store,” said Paul Kefassi, the co-founder of Rogue Amoeba, maker of Airfoil and other popular Mac software. That doesn’t mean he’s not worried, he said. “Apple has never come out and said we’re committed to software outside the App Store. That secrecy means there’s always some part of us that has to be worried about it.”

Even Apple’s power over iOS software downloads has also been challenged in recent weeks, with the European Commission questioning whether the App Store should be the only way users can download software. Several major developers, including the companies behind Tinder and Fortnite, two of the most popular apps, have called out Apple for the way it controls its system, criticism that was once rare from the people who depend on the company for their livelihoods.

Mike Sax, chairman and founder of the App Association, an industry group funded in part by Apple, said he didn’t believe Apple’s switch to ARM chips would give Apple more power. On the contrary, he said it was “amazing” how seamless the transition will likely be. “They’re basically replacing the guts of these computers mid flight but everything will continue working,” he said.

Intel, in a written statement Monday, said Apple was still a customer across several areas of business and it would continue to provide support. It said Intel chips were “the most open platform for developers, both today and into the future.”

The move to Arm chips comes amid a big shift in Apple’s business model. As sales of iPhones have slumped, Apple has been expanding its services business, which includes revenue it makes on its App Store. Wall Street analysts are keeping a close watch on exactly how much Apple’s services revenue grows and at what pace. And of course, the move to Arm chips also reduces what Apple pays to Intel for chips.

Apple, which is valued by investors at more than $1.5 trillion, didn’t say anything Monday about how the move to Arm might help it eke more revenue out of developers or reduce costs. “As always with Apple it’s never what you see on the surface,” Blix’s Volach said.