Apple has released the fourth developer betas of iOS 3, tvOS 3, macOS 10.14.5, and watchOS 5.2.1. Interestingly, the Cupertino-based company also announced the Public betas of these versions to the testers, however, the public beta of the watchOS 5.2.1 isn't yet available. The fourth developer betas of the mentioned operating system versions come almost a week after Apple issued the third public betas.

The new beta builds can be acquired by developers enrolled in the testing program as an over-the-air update on devices or via the Apple Developer Center. And, the Public beta versions of each beta operating system release can be gained via the Apple Beta Software Program website.

The fourth beta of iOS 12.3 is build 16F5148a; Build four of tvOS 12.3 is build number 16M5146a, up from 16M5139a. The latest watchOS 5.2.1 build is 16U5110a. Lastly, macOS 10.14.5's fourth build is 18F127a, replacing the third build 18F118d.

The tvOS 12.3 and iOS 12.3 beta 4 brings the new version of TV app which is updated with a new look and UI. The updates bring a new algorithm-based curator that suggests which movies and TV shows you should watch based on watch history and user’s overall preferences. The updated TV app includes a fresh look and has the “Watch Now” section with the “Up Next” feature for keeping track of the TV shows.

Apple recommends users avoid installing betas on to their primary devices due to the potential data loss or other issues. It’s, therefore, recommended to install the betas onto secondary or non-essential devices.