Landmark EU rules will finally put regulation of Big Tech to the test

Imagine an online world where what users want matters, and interoperability reigns. Friends could choose whichever messaging app they like and seamlessly chat cross-app. Any pre-installed app could be deleted on any device. Businesses could finally access their Facebook data, and smaller tech companies could be better positioned to compete with giants. Big Tech could even face consequences for not preventing the theft of personal info.

As the US struggles to pass legislation to protect Internet consumers, in the EU, these ideals could become reality over the next few years. EU lawmakers...