Google, Microsoft, Amazon, and Taboola are paying the owner of Adblock Plus to unblock ads on their websites at a fee of "30% of the additional ad revenues" they would have made were ads unblocked, the Financial Times reports.

Adblock Plus is the most popular browser extension to block advertising and has been downloaded more than 300 million times. The free service says on its website that it blocks "annoying" banners, pop-ups, and video ads. Eyeo, the German company that owns Adblock Plus, says the add-on has more than 50 million monthly active users.

Ad blocking is an existential threat to internet services who rely on advertising for most of their revenues. As the Financial Times points out, German media groups including RTL and ProSiebenSat.1 are seeking damages from Eyeo.

To block all ads, Adblock users must go into the software settings and configure them to the strictest options possible.

Eyeo's business model operates around its "whitelist" service, which allows some ads to appear to Adblock Plus users. That whitelist consists of only "acceptable ads" that meet criteria such as being transparent about the fact they are advertising and not disrupting or distorting page content.