Adblock Plus, the world’s most popular ad-blocking tool, today announced it has passed 500 million downloads. The half-a-billion milestone was achieved after 10 years: It just so happens that this is the same week that Wladimir Palant wrote Adblock Plus 0.6 for Mozilla Firefox back in 2006.

It’s important to emphasize that the company is highlighting downloads, not active users. Adblock Plus didn’t share an update on the number of active users it has.

According to the most-recently shared numbers, Adblock Plus has over 50 million active users while AdBlock, another popular ad-blocking solution, has over 40 million active users. Both tools are available across multiple platforms, so keep in mind that these numbers span various types of devices.

Adblock Plus took the opportunity today to give an account of the last decade. The most interesting part is the very beginning:

The first ad blocker was written by a guy named Henrik Aasted Sørensen. It didn’t really gain much popularity outside tech circles, though, and eventually the code was ignored and passed around to a few different developers. No one really stuck with it till 2006, when Wladimir Palant rewrote it.

“I thought that I would quickly improve Adblock, make it good enough to become the #1 extension — and be done with it,” Palant explained. “Didn’t quite work out the way I hoped, turned out that with projects like that there is always something to do. Ten years went by and I’m still busy with it.”

Eyeo, the Germany-based company behind the Adblock Plus software, now employs 49 people from 17 different countries. In addition to maintaining the actual ad-blocking tool, the team helps manage its Acceptable Ads initiative, which selectively blocks advertising. Nonintrusive ads (the whitelist now has over 700 entities) are allowed through in an attempt to find a compromise between users and advertisers.

That list has had an interesting impact on the advertising industry, though the company doesn’t share what percentage of users keep it on. Still, with 50 million users across the desktop (Firefox, Chrome, Opera, Safari, IE) and mobile (Android and iOS), Adblock Plus has a massive reach that the advertising industry can’t ignore. We’d bet it will take the tool less than 10 years to pass 1 billion downloads.