Apple has announced an increase in the number of testers that developers can invite to test their apps through TestFlight. Starting today, developers can invite up to 2,000 testers through TestFlight, doubling the capacity from the previous 1,000 tester limit. From Apple:

Now you can invite up to 2,000 users to beta test your iOS and tvOS apps before you release them on the App Store. TestFlight makes it simple to invite testers using just their email address and lets testers easily provide valuable feedback within the TestFlight app

The increase was originally announced at this year's Worldwide Developers Conference, but Apple has now flipped the switch. In addition, TestFlight beta build expiration time has now increased from 30 days to 60 days; another change that was announced at WWDC.

Source: Apple