Legislation that will forever change the Internet and significantly complicate the life of technological giants will come into effect tomorrow. The European Union’s Digital Markets Act (DMA) comes into effect on November 1, starting a countdown to a process expected to force Amazon, Google and Meta to make their platforms more open and interoperable by 2023, reports ArsTechnica. This could lead to significant changes in what people can do with their devices and apps, and it will serve as yet another reminder that Europe regulates tech companies much more heavily than the US.

“We expect the consequences to be significant,” says Gerard de Graaf, a veteran EU official who helped pass the DMA early this year. Last month, he became director of a new EU office in San Francisco, established in part to explain the law’s consequences to Big Tech companies. De Graaf says they will be forced to break open their “walled gardens”.

“If you have an iPhone, you should be able to download apps not just from the App Store but from other app stores or from the Internet,” says de Graaf.

DMA requires dominant platforms to let in smaller competitors, and could force Meta’s WhatsApp to receive messages from rival apps like Signal or Telegram, or prevent Amazon, Apple and Google from favoring their own apps and services.

Although the DMA takes effect next week, technology platforms are not required to comply immediately. First, the EU must decide which companies are large and entrenched enough to be classified as gate keepers, subject to the strictest rules. De Graaf expects about a dozen companies to join the group, which will be announced in the spring. These gatekeepers will then have six months to bring their activities into compliance.

De Graaf predicted a wave of lawsuits challenging new European rules for big tech, but says he is in California to help explain to Silicon Valley giants that the rules have changed. According to him, the EU previously levied large fines against Google, Apple and other companies as part of antitrust investigations, a mechanism that placed the burden of proof on bureaucrats. Under the DMA, the burden of responsibility rests with the business. “The key message is that negotiations are over, we’re in a compliance situation,” de Graaf says. “You may not like it, but that’s the way it is.”

Like the EU’s digital privacy law, the GDPR, the DMA is expected to lead to changes in how technology platforms serve people beyond the EU’s 400 million internet users, as some details of compliance will be easier to implement on a global scale.

Tech companies will also soon have to deal with a second sweeping EU law, the Digital Services Act, which requires risk assessments of some algorithms and disclosures about automated decision-making and could force social apps like TikTok to open up their data to external scrutiny. The law will also be phased in, with the largest online platforms expected to comply by mid-2024. The EU is also considering the possibility of adopting special rules on artificial intelligence, which could prohibit some cases of use of this technology.