Adblock Plus creator Eyeo has revealed crucial details behind the operation of the company’s controversial “acceptable ads” programme, which allows some advertisements through its adblocking software, often in exchange for a cut of the revenue received from the ads.

In a blogpost, the company explained how it decides which publishers are asked to pay a fee to let their adverts through, and gave a partial explanation as to how that fee is calculated. Adblock Plus is the most popular desktop adblocking software, and its database is also used for many popular mobile adblocking apps (such as the iOS and Android app Crystal), which also integrate the acceptable ads program.

“Only advertisers that stand to gain more than 10m incremental ad impressions per month because of whitelisting are asked to sponsor,” the blogpost explained. “To put that in perspective, if 5% of a site’s users block ads, for example, then that site needs to have 200m ad impressions to begin with in order to break the 10m threshold.”

The company estimates that 90% of the members of the acceptable ads programme don’t meet that threshold, and thus see their ads whitelisted for free. But for those that are earmarked for a fee (in Eyeo’s parlance, “asked to sponsor” the service) that fee “normally represents 30% of the additional revenue created by whitelisting its acceptable ads”.

To be whitelisted, publishers also have to meet another requirement, beyond paying a fee or being small: their adverts have to be deemed “acceptable”. That means they must follow guidelines set by Eyeo and its community of adblockers about placement, design and resource use, but the final say over whether a publisher’s ads are acceptable is made exclusively by Eyeo.

This is due to change in the immediate future, with Eyeo “laying the foundation” for a committee to take over the acceptable ads programme. The firm still hasn’t revealed who will be on the committee, citing “NDAs and contracts”, but says it will involve “independent players from the ad industry, from nonprofits and from tech”.

The acceptable ads programme has been controversial, drawing Eyeo and Adblock Plus criticism from both users and publishers. The former complain that an adblocker that doesn’t block every advert by default isn’t fit for purpose, and argue that Eyeo has compromised its integrity by taking payment from those who it is supposed to be opposing.

The latter, meanwhile, have condemned the programme as a “protection racket”. German media group Axel Springer even sued over the scheme, although only after an earlier lawsuit on more conventional grounds had failed. That lawsuit, which Springer eventually lost, was followed shortly after by Adblock Plus’ announcement that the acceptable ads scheme would be independently overseen.