A pop-up blocker is a function or a program that prevents additional browser windows, known as pop-ups , from being opened. The function is included in many modern web browsers and, with older models, can also be installed subsequently as a plug-in extension or directly on a proxy server .
The latter also reduces the amount of data to be transferred and can therefore accelerate the opening of the website. The disadvantage for webmasters is declining advertising revenue, as pop-ups are mainly used to display advertisements. In spite of sophisticated filtering techniques, intervention by the user is occasionally necessary when actually desired popups are blocked that actually did not contain any advertising.
Most programs of this kind are also equipped with more or less extensive filter rules that allow pop-ups to be blocked only from certain pages ( blacklist ) or, conversely, only from certain pages ( whitelist ).