How To Update Macos High Sierra 10.13.6 To 10.15 Jun 2026

The Complete Guide: How to Update macOS High Sierra 10.13.6 to macOS 10.15 (Catalina) If you’re still running macOS High Sierra 10.13.6 , you’re likely missing out on years of performance improvements, security patches, and modern features. Moving to macOS Catalina (10.15) represents a significant leap forward, introducing Sidecar (iPad as a second display), Screen Time, redesigned Apple Music and Podcasts apps, and the death of iTunes in favor of Finder-based device syncing. However, this is not a “simple click update.” Because you are skipping two major OS versions (Mojave and Catalina), there are critical compatibility checks and preparation steps you must take before pressing the upgrade button. This long-form guide will walk you through every stage: pre-upgrade checks, data backup, compatibility verification, the actual installation process, and post-upgrade troubleshooting.

Part 1: Is Your Mac Even Eligible for Catalina? Before you spend an hour preparing, let’s ensure your hardware supports macOS Catalina. Apple dropped support for many older Macs in 10.15. Your Mac must be one of the following models:

MacBook: Early 2015 or newer MacBook Air: Mid 2012 or newer MacBook Pro: Mid 2012 or newer Mac mini: Late 2012 or newer iMac: Late 2012 or newer iMac Pro: 2017 (all models) Mac Pro: Late 2013 or newer

How to check your model: Click the Apple logo (top-left) → “About This Mac.” Under the “Overview” tab, you’ll see the model and year. If your Mac is from 2012 or later (except 2012 Mac Pro cheese grater), you’re likely fine. how to update macos high sierra 10.13.6 to 10.15

Warning: If your Mac is older than 2012, you cannot install Catalina natively. Your final supported version is High Sierra (10.13.6) or Mojave (10.14) on some 2010-2011 models with patchers – but that’s beyond this guide.

Part 2: Crucial Pre-Update Preparation (Do Not Skip) Moving from 10.13.6 to 10.15 is a major system overhaul. The installer completely rewrites your system partition and upgrades the file system structure (though you’re already on APFS if you updated High Sierra after a certain point). Here’s how to prepare. 2.1 – Back Up Everything – Twice This is the golden rule. Catalina changes how system files are stored (read-only system volume) and can occasionally fail, leaving your Mac unbootable.

Time Machine Backup: Connect an external drive. Go to System Preferences → Time Machine → Select Backup Disk → “Back Up Automatically.” Force a backup: Click the Time Machine icon in the menu bar → “Back Up Now.” Bootable Clone (Advanced): Use a free tool like SuperDuper! or Carbon Copy Cloner to create a bootable backup on a separate external drive. This allows you to run your old High Sierra directly from the external drive if disaster strikes. Manual Data Copy: At minimum, copy your Documents, Desktop, Downloads, Music, Pictures, and any application support folders to an external drive or cloud storage. The Complete Guide: How to Update macOS High Sierra 10

2.2 – Audit Your 32-Bit Applications (Major Breaking Change) Catalina does not support 32-bit applications. Period. If you have any old software from 2015 or earlier that hasn’t been updated, it will simply refuse to open after the upgrade. How to check for 32-bit apps on High Sierra:

Go to Apple menu → About This Mac → System Report. Scroll down to “Software” → “Applications.” Wait for the list to populate. Look at the “64-bit (Intel)” column. If it says “No,” that app will die on Catalina.

Common 32-bit casualties:

Older Adobe Creative Suite (CS6, CS5, etc.) Microsoft Office for Mac 2011 Many legacy games (StarCraft original, Diablo II, etc.) Old printer drivers

Action Plan: Find 64-bit replacements before upgrading, or accept that you’ll lose access to those apps. If you rely on any legacy 32-bit apps, do not upgrade to Catalina – stay on High Sierra or Mojave. 2.3 – Free Up Disk Space The Catalina installer is about 8 GB, but it requires up to 20-25 GB of free space to unpack and install. You’ll need even more for smooth operation afterward. Recommended free space: 30 GB minimum. How to clean up High Sierra: