Apple is continuing to roll out new builds of its developer betas, with a new fifth build of iOS 12.4 joined by the fourth build watchOS 5.3 and the third build of macOS 10.14.6 now available for testing.
The new builds can be acquired by developers in the beta as an over-the-air update on devices already enrolled into the program, or through the Apple Developer Center. Public beta variants of each operating system normally surface a few days after the developer betas, and can be accessed from the Apple Beta Software Program website.
Apple's fifth iOS 12.4 build is 15G5056d, replacing the fourth build 16G5046d. The fourth watchOS 5.3 build is 16U5558b, up from the third beta, build 16U5545c. Lastly, the third macOS 10.14.6 beta is build number 18G59b, while the second was 18G48f.
There have yet to be any real changes found in the operating systems, suggesting the updates are more for performance improvements and bug fixes, as well as background preparations for upcoming products or services.
Apple is concurrently running developer betas for iOS 13, tvOS 13, watchOS 6, and macOS 10.15 concurrently to the earlier betas.
AppleInsider, and Apple itself, strongly suggest users don't install the betas on to what they could describe as "mission-critical" or primary hardware, as there is the small possibility of data loss or other problems. Instead, testers should install betas onto secondary or non-essential devices, and to ensure there are sufficient backups of data before updating.