how do websites know you have adblockers installed

[jag]

I never have used an adblocker asking for a friend.

[tacnet]

Its relatively easy

One way would be to try and load a small iframe somewhere with the word "banner" or "add" in the url. Then use javascript to test whether that iframe was loaded. If not then the user has likely got an add blocker installed

[Gaming_Mike]

Good point Tacnet naming directories or sub-domains called banners or ads is not a good idea.

[alsporn]

You know what pisses me off is when I see porn sites promoting ad blockers.

[AlexO]

You know what pisses me off is when I see porn sites promoting ad blockers.

Only dumb fuckers would promote ad blockers

[Franksdomains]

You know what pisses me off is when I see porn sites promoting ad blockers.

Only dumb fuckers would promote ad blockers