Very likely probing user client state to detect ad-blockers without consent is illegal in EU law. Directive 2002/58/EC legal text: 3. Member States shall ensur

Very likely probing user client state to detect ad-blockers without consent is illegal in EU law. Directive 2002/58/EC legal text: 3. Member States shall ensure that the use of electronic communications networks to store information or to gain access to information stored in the terminal equipment of a subscriber or user is only allowed on condition that the subscriber or user concerned is provided with clear and comprehensive information in accordance with Directive 95/46/EC, inter alia about the purposes of the processing, and is offered the right to refuse such processing by the data controller. This shall not prevent any technical storage or access for the sole purpose of carrying out or facilitating the transmission of a communication over an electronic communications network, or as strictly necessary in order to provide an information society service explicitly requested by the subscriber or user. Alexander Hanff has been fighting the fight to make this a reality and recognized by courts. Mainstream media coverage of the story: https://www.theverge.com/2023/11/7/23950513/youtube-ad-blocker-crackdown-privacy-advocates-eu https://www.theverge.com/2023/11/7/23950513/youtube-ad-block... Not only it is illegal, it's also not at all how HTTP was designed to work. If a business use case makes it so that the system doesn't want to serve a request, the server can (and should) return one of 4xx error messages. Returning with OK and then doing invasive malware-esque data mining is not A-OK.