Mozilla Warns: Ad Blockers Could Become Illegal in Germany

Red Dog Security

— 2 min read
Mozilla Warns: Ad Blockers Could Become Illegal in Germany

Mozilla representatives report that a recent ruling by Germany's Federal Court of Justice (BGH) has reignited an old legal dispute over whether browser-based ad blockers violate copyright law. The organization warns this development could eventually lead to a ban on such tools in the country.

This case traces back to a lawsuit filed by German media conglomerate Axel Springer against Eyeo, the company behind the popular extension Adblock Plus.

Axel Springer’s portfolio includes well-known outlets such as Bild, Die Welt, Business Insider, Politico, Morning Brew, and Idealo. Most of these platforms depend heavily on advertising as their primary revenue stream. The company argues that ad blockers pose a direct threat to this model.

According to Springer, the mere act of rendering websites in a browser may constitute copyright infringement. Their claim rests on the idea that website code (HTML and CSS) is a protected computer program, and that ad blockers interfere with the process by altering execution structures in memory—such as the DOM, CSSOM, and rendering tree. Under this reasoning, such interference could be classified as unauthorized reproduction or modification of copyrighted material.

Previous Court Rulings

German courts have addressed this argument before. The Hamburg District Court and later an appellate court rejected the notion that ad blockers interfere with website code, instead describing them as a matter of user choice.

In 2018, the BGH upheld that position, ruling that both the use of ad blockers and the "whitelist" business model were lawful. The court noted that:

  • Users install extensions voluntarily.
  • Publishers remain free to restrict access for visitors using such tools.

This decision was widely seen as a victory for consumer rights and digital freedom.

The July 2025 Reversal

On July 31, 2025, however, the BGH changed course. The court overturned the appellate decision and sent the case back for reconsideration. This time, judges emphasized the need for a deeper technical review:

  • What specific changes ad blockers make to code execution.
  • Whether such code qualifies as protected under copyright law.
  • Under which circumstances interference may still be considered lawful.

For Mozilla, the implications are clear: if courts ultimately side with Axel Springer, browser-based ad blockers could face a legal ban in Germany, reshaping how millions of users experience the internet.

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