In an investor conference call following Apple's release of fiscal quarter three earnings on Thursday, Cook said some four million people are running beta software on their iPhone, iPad, Mac, Apple Watch and Apple TV devices. 

"In June, we hosted an extremely successful developers conference that previewed many major advances coming this fall to our four operating systems: iOS, macOS, watchOS and tvOS," Cook said. "Developer and customer reaction has been very positive and we have over four million users participating in our new OS beta programs."

The number of beta program participants is not something that Apple typically releases, so it's unclear how that number compares to past years. Also unknown is how the participation statistics break down by operating system, and whether developers are included in the number. 

Apple frequently touts both the growth of the App Store and its contributions to the app development profession as a whole, so it's a good guess that the four million figure for software beta participants in one year is among the largest ever for Apple, if not for the history of computing altogether. 

At WWDC, Apple unveiled iOS 12, Mac OS 10.14, watchOS 5 and TV OS 12, and has periodically released beta editions of each in the weeks since. The full releases are scheduled for this fall. 

Source: appleinsider