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Apple has released macOS Catalina 10.15.3, which includes bug fixes and security updates to the Mac Catalina operating system.

Separately, Mac users running Mojave or High Sierra will find new Security Updates available for those respective operating systems.

Additionally, iOS 13.3.1 and iPadOS 13.3.1 were released as updates, along with watchOS 6.1.2 for Apple Watch, and tvOS 13.3.1 for Apple TV.

How to Download & Install MacOS Catalina 10.15.3 Update

Be sure to backup the Mac with Time Machine before installing any system software update.

  1. Go to the Apple  menu and choose “System Preferences”
  2. Select the “Software Update” preference panel
  3. Choose to update to macOS 10.15.3 Catalina when it is shown as available for install

MacOS Catalina system software updates require a notable amount of free storage space available, and the computer must reboot to complete installation.

Recall that MacOS Catalina 10.15.3 updates are only available on a Mac that is already actively running MacOS Catalina.

For Macs running prior system software versions like macOS Mojave 10.14.6 or MacOS High Sierra 10.13.6, there will be Security Updates and Safari updates available to download instead through the system Software Update section of MacOS.

The availability of security updates for older MacOS releases is particularly useful to know if a Mac is ignoring MacOS Catalina software update for compatibility or any other reasons.

Download Links for MacOS Catalina 10.15.3 & Security Updates 2020-001 for Mojave & High Sierra

Another possibility is to install MacOS Catalina 10.15.3 (or the security updates) with a combo update or package update files. Using combo updates for MacOS is easy is much like installing a standard app package on the Mac and is fairly easy, nonetheless you’ll still want to backup before doing so.

MacOS Catalina 10.15.3 Release Notes

Release notes accompanying Catalina 10.15.3 are fairly brief, but presumably there are other bug fixes and enhancements included in the release.

The ‌macOS Catalina‌ 10.15.3 update improves the stability, reliability and security of your Mac, and is recommended for all users.

This update:
– Optimizes gamma handling of low gray levels on Pro Display XDR for SDR workflows when using macOS

– Improves multi-stream video editing performance for HEVC and H.264 encoded 4K video on the 16-inch MacBook Pro (2019)

The release notes accompanying the security updates for Mojave and High Sierra are even simpler.