Apple has released iOS 12.1.3 beta 3 to developers and public beta testers who are running beta system software on their compatible iPhone or iPad.
The newest iOS beta likely focuses on various bug fixes and security updates, and is unlikely to include any major new features or sweeping changes.
Separately, Apple has also release the third beta version of tvOS 12.1.2 and watchOS 5.1.3. Currently absent from the beta updates is any update to macOS Mojave 10.14.3, which is still at beta 2.
Users who are enrolled in the iOS beta testing program can find iOS 12.1.3 beta 3 available to download now from the Software Update section of the Settings app.
Users enrolled in the watchOS and tvOS beta testing programs can find the beta updates available through their respective Settings update mechanisms as well.
Apple usually goes through a variety of beta versions before releasing a final version of system software to the public.
The most recently available final stable builds of system software for the Apple lineup is currently iOS 12.1.2, MacOS 10.14.2, tvOS 12.1.1, and watchOS 5.1.2.