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Executive Summary
• Ad blocker detection is not illegal, but might, under a strict interpretation of the ePrivacy Directive be regulated and require the informed consent of users.

• Depending on the technical implementation of ad blocker detection, such detection may be out of scope of the consent requirement of the ePrivacy Directive, or fall within an exemption to the consent requirement. But the legal situation is not very clear.

• Publishers who use ad blocker detection should update their privacy policy to
include use of ad blocker detection scripts.

• Publishers may want to err on the side of caution and obtain consent for the use of ad blocker detection scripts to preempt and avoid any legal challenges.

• Publishers could obtain consent by slightly modifying their existing compliance mechanisms for the use of cookies as the possible new consent requirement
emanates from the same law mandating consent for the use of cookies.

• Publishers could use two practical solutions to request and obtain consent for
the use of ad blocker detection: a consent banner or a consent wall.
Publishers could also make use of a combination of the two to complement
each other.

Source