OS X 10.11.3 Beta 2 Available for Testing
Apple has released the second beta build of OS X 10.11.3 for users in both public and developer Mac beta testing programs. The new build arrives as 15D13b and presumably focuses on bug fixes and feature improvements, it’s unlikely that any new features are to be included.
Mac users currently participating in the respective beta testing programs and running a prior OS X beta build can find the latest OS X 10.11.3 beta 2 download available from the Mac App Store in the Software Update section.
Anyone can enroll to participate in the public beta program, but it’s generally not advised for most users as beta system software is buggier and less reliable than stable releases. The developer beta build is the same version, but only available to users who are registered with Apple as an official Apple Developer, which also allows them to gain access to iOS beta releases.
For those who enjoy beta testing system software, Apple has also released iOS 9.2.1 beta 2 for iPhone, iPad, and iPod touch.
There is no known public launch timeline for OS X 10.11.3 but typically Apple goes through multiple beta releases before offering a final version to the general public.