How To Update Macos High Sierra - 10.13.6 To 10.15
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.
The Final Leap: Updating from macOS High Sierra 10.13.6 to Catalina 10.15
For users still running macOS High Sierra (10.13.6), moving to macOS Catalina (10.15) represents a significant architectural shift. This is not a minor patch but a complete operating system upgrade that changes how your Mac handles apps, media, and security. how to update macos high sierra 10.13.6 to 10.15
However, unlike modern macOS versions (Ventura, Sonoma, Sequoia), upgrading from High Sierra to Catalina can be technically tricky because Apple has removed the direct "Software Update" path for many older machines. Here is the definitive guide to making the jump.
Final Warning: The End of the Road
If your Mac is stuck on High Sierra because it lacks Metal graphics, do not try to force Catalina via patches (like DosDude1’s patcher). While possible, those patched systems are highly unstable on modern internet services in 2026.
Instead, consider staying on High Sierra but switching to a security-focused browser (like Firefox ESR) or upgrading your hardware. Catalina is dead software; Apple stopped supporting it in 2022. If you want real security, you need macOS Monterey (12) or newer. The Complete Guide: How to Update macOS High Sierra 10
Summary: If you have a 2013+ Mac with an SSD and no 32-bit apps, download the installer from Apple’s legacy URL, backup, and run the installer. If not, stay on High Sierra.
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:
- Empty Trash.
- Use “Storage Management” (Apple menu → About This Mac → Storage → Manage).
- Delete large old iOS backups (found in ~/Library/Application Support/MobileSync/Backup/).
- Remove unused applications.
- Use a tool like OmniDiskSweeper (free) to visualize space hogs.
5.5 – Reset Permissions and PRAM/NVRAM (Optional but helpful)
If you notice odd behavior (Wi-Fi dropping, sound glitching):
- Shut down → Turn on and immediately press Cmd + Option + P + R → Hold for 20 seconds (or until you hear second startup chime on older Macs).
Troubleshooting: What If Updating Fails?
Step 6: Final Setup Assistant
After the final reboot, you’ll see a “Welcome to macOS” screen. Follow the prompts: The Final Leap: Updating from macOS High Sierra 10
- Sign into iCloud (same Apple ID).
- Set up Screen Time (optional – you can skip).
- Choose dark or light appearance.
- Migrate data from Time Machine backup (only if this is a clean install; but you’re upgrading, so say “Not now”).
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.
