Following today's iOS 9.2.1 beta release, Apple issued the first version of OS X 10.11.3 El Capitan to developers with minor improvements and bug fixes.
Aside from the usual stability, compatibility and security updates, the seed notes accompanying build 15D9c do not provide a detailed rundown of the exact changes included in today's OS X 10.11.3 beta release. A more detailed list, as well as focus areas for testing, should be included in the second beta release.
Apple's last update for the Mac operating system, OS X 10.11.2, dropped last week with a handful of improvements relating to Wi-Fi reliability, Handoff and AirDrop, Mail issues and iCloud Photo Sharing for Live Photos. The release also addressed a number of minor usability issues, bugs and security flaws.
The OS X 10.11.3 beta is the third seed to see release hit in as many months. Apple issued OS X 10.11.1 in late October, about one month after El Capitan debuted on Sept. 30.
Developers can download OS X 10.11.3 from the Mac App Store or Apple's developer portal.