Ad blockers, once seen as a niche browser tool, have become the center of a long-running clash between internet users and publishers. What began as a fight between users wanting freedom from intrusive ads and publishers wanting to keep their business model alive has now reached a pivotal moment in Germany’s highest court.

Germany’s Federal Supreme Court (BGH) has reopened a case that could ultimately ban ad blockers in the country. The case involves media powerhouse Axel Springer and Eyeo, the Cologne-based company behind Adblock Plus, one of the world’s most popular ad-blocking tools.

The Case

Axel Springer, which owns major outlets like Bild and Welt, argues that websites aren’t just text and pictures — they are also made up of code that counts as a protected computer program. It further argues that when an ad blocker hides an advertisement, it is actually illegally interfering with the underlying code that builds a website inside a browser without permission. Meanwhile, Eyeo insists that it is simply letting users decide what to see.

Earlier, a lower court in Hamburg wasn’t convinced and had dismissed this argument. But on July 31, 2025, the BGH overturned parts of that ruling, saying judges hadn’t properly examined whether browser code like the Document Object Model (DOM) and CSS Object Model (CSSOM) are legally protected works — and if hiding ads amounts to unauthorized tampering.

“It cannot be excluded that the bytecode, or the code generated from it, is protected as a computer program, and that the ad blocker, through modification or modifying reproduction, infringed the exclusive right thereto,” reads BGH’s statement (automated translation)

The case is now being sent back to the Hamburg lower courts for deeper technical scrutiny.

Why It Matters

The implications stretch far beyond advertising. If courts agree with Springer’s view, it could mean that any browser extension that modifies websites—from privacy filters to accessibility tools—would be considered illegal. This could impact not only ad blockers, but also tools designed to improve accessibility, strengthen security, or prevent online tracking.

Mozilla, the maker of the Firefox browser, has warned that this could make Germany the first democratic country to outlaw ad blockers – a move it says would harm user freedom, innovation, and online privacy.

In a statement, Daniel Nazer, Mozilla’s Senior IP & Product Counsel, said that the ruling risks creating a “chilling effect” with browsers locking down features and extension developers pulling back to avoid lawsuits.

“We sincerely hope that Germany does not become the second jurisdiction (after China) to ban ad blockers. This will significantly limit users’ ability to control their online environment and potentially open the door to similar restrictions elsewhere. Such a precedent could embolden legal challenges against other extensions that protect privacy, enhance accessibility, or improve security,” added Nazer.

What’s Next 

The case is far from over, as it now returns to Hamburg’s lower courts, where further hearings could stretch on for years. Until then, ad blockers remain legal in Germany —but no one can say for sure how long that will last.