YouTube’s ad blocker detection technology is facing legal challenges from privacy advocates who claim it violates their privacy rights under the General Data Protection Regulation (GDPR). According to the complaint, YouTube violates users’ privacy by using JavaScript-based detection scripts to look for specific HTML page elements rendered by a user’s browser. YouTube began rolling out adblocker detection to European markets earlier this year, and the site is now preventing some European users from viewing its content if they have an adblocker enabled.

The anti-adblocking JavaScript allegedly runs on the users’ local device to identify whether it is also running specific software – namely, whether the user is using an adblocker. Because this processing happens on the users’ computer, rather than on YouTube’s servers, activists claim that it violates the GDPR’s requirement that service providers get explicit permission to “gain access to information stored in the terminal equipment of a subscriber or user.”

Activists have petitioned the European Commission to determine whether this implementation of adblocking technology is “absolutely necessary to provide a service such as YouTube.” The Irish Data Protection Commissioner’s Office is also investigating YouTube’s use of adblocker detection.

YouTube’s current terms do not explicitly mention the use of ad-blocking tools or any detection measures. Activists argue that EU courts would hold such provisions invalid under the GDPR as a violation of privacy rights.