Apple today seeded the third beta of an upcoming macOS Sierra update to developers for testing purposes



From MacRumors:

macOS Sierra 10.12.1 appears to focus on bug fixes and under-the-hood performance improvements to address issues that have been found since the operating system's release. Few outward-facing changes were discovered in the first two betas, but it does include Photos support for the new iPhone 7 Plus Portrait feature introduced with iOS 10.1. New features discovered in the third 10.12.1 beta will be listed below.

  Apple Seeds Third macOS Sierra 10.12.1 Beta to Developers