I believe installed extensions are directly query-able through javascript or html5
The requirement for this is that those extensions need to directly interact with - and respond to - page elements.
Security add-ins are a “black hole” in that the vast majority of them only block, they don’t interact. There is absolutely no way for a website to tell which ad-blocker is installed from purely the ad-blocking component itself. Provided the add-on is constructed properly, it should never respond to any code either on the client-side or server-side, it should only block the browser from not even requesting certain assets in the first place. In fact, a good adblocker should be indistinguishable from a failure of DNS in providing the IP address of the ad server.
The requirement for this is that those extensions need to directly interact with - and respond to - page elements.
Security add-ins are a “black hole” in that the vast majority of them only block, they don’t interact. There is absolutely no way for a website to tell which ad-blocker is installed from purely the ad-blocking component itself. Provided the add-on is constructed properly, it should never respond to any code either on the client-side or server-side, it should only block the browser from not even requesting certain assets in the first place. In fact, a good adblocker should be indistinguishable from a failure of DNS in providing the IP address of the ad server.