Like iOS 9.3 beta 7, we expect this seventh beta of OS X 10.11.4 to be last test build. Apple will likely release final version of OS X 10.11.4 to public along with iOS 9.3, tvOS 9.2 and watchOS 2.2 at its March 21st media event where the company is also expected to unveil its 4-inch iPhone SE, 9.7-inch iPad Pro, and new bands for Apple Watch.
Carrying build 15E64a, the seventh beta of OS X 10.11.4 adds in the usual stability improvements and fixes for any last showstopper bugs before the final consumer release. OS X 10.11.4 is generally considered as a minor update to OS X 10.11 and features Live Photos support in Messages app, password protection for the stock Apple Notes app, among other things. Apple’s main focus with OS X 10.11.4 update has been to bring under-the-hood performance improvements and stability to Macs.
If you are already running any previous beta seed of OS X 10.11.4, you can grab the latest beta update from under Updates tab on the Mac App Store.
If this is the first time you are installing any OS X beta, you can download it either from developer.apple.com (Apple Developer Program) or beta.apple.com (Apple Public Beta Program).