Microsoft may have just acquired developers’ favorite code repository GitHub, but it is Apple where many of them are making a lot of money at the moment. Today at WWDC, Apple’s CEO Tim Cook announced that there are now 20 million registered developers on iOS, and collectively they have made about $100 billion in revenues, with the App Store bringing in some 500 million visitors per week.

“We’re also happy to announce that this week we’re going to achieve another huge milestone,” Cook said in his presentation. “The money that developers have earned through the App Store will top $100 billion.”

The figures underscore how Apple’s attention has continued to swing more firmly into its developer ecosystem and app marketplace, which is becoming a stronger engine of revenue generation as overall smartphone purchasing slows down in more saturated markets.

He also said that Swift, the programming language Apple developed and uses for its apps, is also picking up some strong momentum.

“It’s the fastest growing programming language out there,” he said. “Apple developers are using it in huge numbers, in fact over 350,000 apps have been written in Swift in the app store. We believe that coding is an essential skill and believe it should be offered by every school in the world. Learning to code has so many benefits, it developers problem solving, critical thinking skills.”