Almost 9% of all Firefox users have the extension Adblock Plus installed and thus block advertisements on websites. The 9% is the equivalent of more than 22 million Firefox users who use the extension, making it the most popular add-on for the open source browser.
The second most popular add-on is McAfee Security Scan Plus detection which is bundled with the installation of Adobe Flash Player and is installed on about 16 million computers. Other add-ons that protect against tracking such as NoScript and Ghostery are installed on respectively 2.3 million and 1.5 million computers, meaning their install base is much smaller than the previous mentioned add-ons. Especially Adblock Plus is a big concern for publishers and websites that depend on advertising revenues.
German media group ProSiebenSat.1 earlier stated that ad blocking costed them 9,2 million last year, according to the Economist. Especially websites that target male tech enthusiasts suffer from ad blockers. The editor in chief of a large Dutch tech site recently reported that 30% of their visitors blocks advertisements.
Some websites, like the online video service Hulu, block users who visit their site using an adblocker. Other websites display an alert, sometimes asking the user to disable the ad blocker or to whitelist the visited website. Other publishers try to tackle the problem by trying out different revenue models, like sponsored content or subscriptions.
According to some researchers the use of ad blocks will nevertheless continue to grow the coming years.
