To Block or Not to Block? German Supreme Court Weighs in on Ad-Blockers

Ad-blockers continue to stir heated debates at the intersection of copyright law and the digital economy. Publishers argue they threaten revenue, while users see them as essential shields against intrusive ads. The German Supreme Court (GSC) recently weighed in on this controversy in the landmark Werbeblocker IV case (I ZR 131/23), examining whether ad-blockers infringe copyright.

Background

A major publisher sued AdBlock Plus, claiming the software illegally reproduced or modified its websites, which rely on embedded ads for monetization. Technically, the ad-blocker works by:

1. Preventing the browser from requesting ads via blacklists.
2. Hiding ad elements in the browser’s Document Object Model (DOM) and related rendering structures.

The lower courts ruled in favor of the ad-blocker, reasoning that it did not alter the “substance” of the publisher’s software; it merely affected temporary data structures generated by the browser (DOM, CSSOM, Render Tree). Claims based on the publisher’s websites as multimedia works were also dismissed.

The Supreme Court Decision

The GSC focused on whether the ad-blocker’s influence on browser-generated structures could constitute a modification of a protected work. Key points:

• The appeal was admissible only regarding whether ad-blockers modify a website’s protected elements.
• Courts must clearly identify the protected code or features before dismissing copyright claims.
• The Supreme Court criticized the lower court for not addressing whether browser-generated code (bytecode converted to object code) might itself be protected and altered by the ad-blocker.

The decision was remitted to the Court of Appeal for further clarification.

What’s Next?

If copyright infringement is found, the Court of Appeal will need to consider several defenses:

1. Does making a website publicly accessible imply consent to reproductions, even if ad-blockers alter the display?
2. Could ad-blocking be necessary for using the website as intended (Computer Programs Directive)?
3. Are ad-blocker actions covered by temporary reproduction exceptions (InfoSoc Directive)?

This ruling marks the GSC’s fourth decision on ad-blockers, and the first to seriously address copyright rather than competition law—potentially shaping the future of online advertising and user rights in Germany.