Apple's WebKit Rule Could Violate New Japanese Law

Growing Pressure on Apple to Allow Browser Engine Diversity

A growing number of jurisdictions are pushing for greater browser engine diversity in the mobile market, challenging Apple’s long-standing restrictions. This movement aims to foster more competition and innovation in the mobile software industry, particularly in how web browsing is handled on iOS devices.

Japan recently introduced new legal guidance as part of its Mobile Software Competition Act, which explicitly prohibits restrictions like Apple’s requirement that apps must use the WebKit framework for web browsing. This law signals a strong stance against monopolistic practices and is expected to take effect in December. The guidelines emphasize that any measures hindering third-party browser engines will not be tolerated.

Apple's current policy, outlined in section 2.5.6 of its App Store Review Guidelines, mandates that all web-browsing apps must utilize the WebKit framework and JavaScript. WebKit is a browser engine similar to Blink (used by Chromium browsers) and Gecko (used by Firefox). Each engine has unique implementations of web standards and APIs, leading to differences in performance, security, and feature support.

This restriction has been a point of contention for developers since it limits the ability of browsers on iOS to differentiate themselves. While browsers like Brave, Chrome, Edge, Firefox, Opera, and Vivaldi offer similar functionalities to Safari, they are constrained by the fact that they all rely on WebKit under the hood. This means that features such as easy home screen installation for Progressive Web Apps (PWAs) are not available, making PWAs less competitive with native iOS apps.

Apple's App Store ecosystem generated nearly $1.3 trillion in billings and sales globally in 2024, giving the company a strong incentive to maintain the dominance of native apps over PWAs. In 2023, Apple initially planned to drop support for PWAs but reversed course after pushback from developers and advocacy groups like Open Web Advocacy (OWA).

Regulators in the European Union and the United Kingdom have also signaled their expectation that Apple should allow non-WebKit browser engines. Apple made this technically possible in iOS 17.4, but neither Google nor Mozilla has yet distributed their browsers in Europe using alternative engines like Blink or Gecko due to ongoing restrictions.

In response, the UK’s Competition and Markets Authority (CMA) proposed designating Apple and Google as "strategic market entities," akin to the EU's "gatekeeper" designation under the Digital Markets Act (DMA). A decision is anticipated in October.

According to OWA, Japan’s guidelines anticipate Apple’s potential compliance and explicitly prohibit measures that could hinder third-party browser engines. This means Apple must not only remove its ban on non-WebKit engines but also avoid practices that make implementing these engines impractical or financially burdensome.

“This is directly relevant to Apple’s current iOS behavior, even under the EU’s Digital Markets Act, where technical and procedural restrictions continue to block meaningful competition,” OWA stated in a blog post. “Japan’s guidance is clearly designed to avoid similar outcomes.”

With the introduction of the Mobile Software Competition Act, Japan is setting a precedent that could influence global regulatory approaches. As more jurisdictions push for browser engine diversity, Apple may face increasing pressure to adapt its policies and promote a more open and competitive mobile ecosystem.