Readers may recall that Japan recently passed the Smartphone Act, officially the Bill on the Promotion of Competition for Specified Software Used in Smartphones. Among its most important reforms is a direct prohibition on Apple’s long-standing ban on third-party browser engines on iOS.

This ban has functioned as an effective ban on browsers like Firefox, Chrome, Edge, Opera, Brave & Vivaldi, by forcing them to use Apple’s WebKit engine, which they cannot modify or control. This results in no effective browser competition on iOS, and web apps being deprived of the APIs and performance they need to compete with native apps.

The legislation was based on the Final Report by Japan’s Headquarters for Digital Market Competition, a report Open Web Advocacy consulted on. Our submission is available here.

Last week, Japan published the Mobile Software Competition Act (MSCA) Guidelines. These subordinate rules clarify how the Act will be interpreted and enforced. Here's what they mean for browser competition.

Ban on Blocking or Hindering Alternative Browser Engines

The guidelines explicitly prohibit any measures that would prevent or hinder the adoption of third-party browser engines:

Actions that "Prevent" the Adoption of Alternative Browser Engines"

Such actions may include: imposing unreasonable technical restrictions on individual app providers while allowing them to adopt alternative browser engines, placing excessive financial burdens on individual app providers for adopting alternative browser engines, and steering smartphone users away from using individual software that incorporates alternative browser engines.

The determination of whether a designated provider's action constitutes "preventing" the adoption of alternative browser engines does not require that it be completely impossible for individual app providers to adopt alternative browser engines. Instead, the determination is made based on the degree of likelihood that such a result will occur.
Mobile Software Competition Act Guidelines
(emphasis added)

This clause is crucial. It means that designated providers (i.e. Apple) must not only eliminate outright bans (like App Store Guideline 2.5.6), but must also refrain from practices that, while technically permitting browser engines, render their use impractical or commercially unviable.

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. Japan’s guidance is clearly designed to avoid similar outcomes.

API Access Must Be Functionally Equivalent

The MSCA also mandates fair access to OS APIs, mirroring Article 6(7) of the EU DMA. For browsers this is particularly critical as they need extensive access to a broad range of APIs typically reserved for Safari and WebKit.

Article 7, Item 2 of this Act prohibits designated providers of basic operation software from preventing other businesses (businesses other than designated providers, etc.) from using OS functions with equivalent performance for the provision of individual software, when such OS functions are used by the designated provider, etc., to provide individual software. By prohibiting actions that prevent other businesses from using OS functions with equivalent performance as utilized by designated providers, etc., for the provision of individual software, this Item aims to promote competition regarding individual software.
Mobile Software Competition Act Guidelines
(emphasis added)

The act does specify that alternative APIs are allowed. However it clarifies that they may not be materially inferior.

However, for example, if other businesses are allowed to use that OS function for individual software provision using a technical method different from that used by designated providers, etc., but the performance is materially inferior to that when designated providers, etc., use that OS function for individual software provision, it does not constitute "other businesses using the equivalent performance to provide individual software".
Mobile Software Competition Act Guidelines
(emphasis added)

Choice Screens

The act also mandates choice screens for browsers among other items. Importantly it specifies that the choice screen must display “Promptly after the first activation", an important improvement on the EU’s Digital Markets Act.

that smartphone users must be made to select a specific individual software from the options displayed on the choice screen promptly after the first activation of the smartphone by the user. "Promptly after the first activation" refers to, for example, displaying the choice screen at the time of initial setup after the first activation of the smartphone, or displaying the choice screen at the time of the first launch of the individual software subject to the choice screen, and making users select a specific individual software from the options.
Mobile Software Competition Act Guidelines
(emphasis added)

What Happens Next?

The Mobile Software Competition Act is expected to come into force by December 2025. With Japan joining the EU and UK, there are now three jurisdictions where Apple will be required to permit browsers to run their own engines. As Japan prepares for enforcement, it is likely studying the regulatory approaches and challenges already unfolding in Europe and the UK.

As the EU and UK have already shown (UK MIR, CMA SMS case, EU DMA enforcement), enforcement will be a long and difficult process.

Now that Japan, the EU, and the UK all require Apple to support third-party browser engines, 2026 may become the decisive year in restoring browser competition on iOS. But much depends on regulators’ resolve, and on Apple’s willingness to comply in substance, not just form.

We’d like to extend our gratitude to the extensive work over many years by the HDMC, JFTC and others in improving browser, browser engine and web app competition.