How To Update High Sierra: Complete Guide To MacOS 10.13 Upgrades

Updating macOS High Sierra (10.13) requires careful verification of your Mac hardware compatibility, a robust local Time Machine backup, and sufficient storage allocation to transition through legacy Apple Software Update mechanisms or the Mac App Store. Because Apple has retired direct distribution for many older operating systems, navigating this update successfully demands specific workarounds, secure root certificate handling, and an understanding of APFS (Apple File System) conversion protocols.

Preparation and System Prerequisites for macOS High Sierra

Executing a successful update or patch deployment on macOS High Sierra demands meticulous planning, as older operating systems lack the modern seamless telemetry and background verification found in contemporary macOS iterations. Neglecting preliminary assessments frequently results in bricked boot volumes, kernel panics, or interrupted file system transitions during the APFS (Apple File System) conversion phase.

• Essential Gear and Utilities: A reliable external hard drive formatted in Mac OS Extended (Journaled) for Time Machine backups, a high-speed stable broadband internet connection, and a reliable USB flash drive with a minimum capacity of 16 GB if you plan to create a bootable installer volume.
• Mandatory Prerequisite Knowledge: Familiarity with Recovery Mode commands, NVRAM/PRAM reset sequences, Target Disk Mode operations, and basic familiarity with using the Terminal application for software catalog overrides.
• Benchmarks and Scope: Allocate a minimum duration of 60 to 120 minutes depending on your internet bandwidth and storage drive speed (mechanical HDD versus solid-state drive), and ensure a minimum of 20 GB of free disk space is permanently available on your boot volume before initiating the installer package.

Step-by-Step Procedure to Update macOS High Sierra

Step 1: Secure Your Data with Time Machine

Before touching any system software or installer packages, you must safeguard your personal files, application states, and preference documents against unexpected power failures or installation halts. Connect your external storage drive, launch System Preferences, click on Time Machine, and select your backup disk to initiate a full system backup.

Warning: Do not skip the backup process. Upgrading from older iterations like OS X El Capitan or Sierra to High Sierra fundamentally restructures the storage architecture into APFS, carrying a minor statistical risk of partition table corruption on aging mechanical drives.

Step 2: Verify Hardware Compatibility and Clean Storage

Ensure your specific Mac model officially supports macOS High Sierra by reviewing Apple's hardware matrix, which covers late-2009 or newer iMacs and MacBook Airs, MacBooks, Mac minis, and Mac Pros, alongside mid-2010 or newer MacBook Pros and Mac Pros. Open About This Mac from the Apple menu to confirm your exact model identifier and available storage capacity.

Pro-Tip: If your startup disk is running low on space, use a dedicated disk cleanup utility or manually clear out the user cache and application logs to ensure you meet the strict 20 GB free space threshold required for temporary installer unpacking.

Step 3: Access and Download the Official Installer

Because newer versions of macOS have displaced High Sierra in the primary Mac App Store search results, accessing the legitimate installer requires using direct, secure update links or navigating your purchase history within the App Store application. Open the App Store, navigate to the Purchases tab, locate macOS High Sierra if previously downloaded, or use a secure web browser to fetch the verified software package payload from Apple's legacy support archives.

Step 4: Execute the Installation and APFS Migration

Double-click the downloaded Install macOS High Sierra application from your Applications folder to launch the graphical installation wizard. Follow the on-screen prompts, accept the software license agreements, select your target boot drive, and enter your administrator credentials to kick off the installation script.

Warning: Your Mac will automatically restart multiple times during this process. Do not force a shutdown or disconnect power while the display shows a blank screen or progress bar, as the machine is actively writing low-level firmware updates and converting your partition map to APFS.

Technical Specifications and Update Matrix

Troubleshooting Common High Sierra Update Failures

Installation Fails Due to Expired Apple Root Certificates

• Root Cause: Apple's legacy security certificates embedded within older installer packages have expired, causing the system to flag the software payload as untrusted or damaged.
• Actionable Fix: Temporarily disconnect from the internet, launch the Terminal application, and use the date command to manually set your system clock back to a date within 2017 or 2018 (e.g., sudo date 061514002017) before running the installer again. Reset your clock to automatic network time once the installation completes.

The Installer Reports Not Enough Free Space

• Root Cause: Hidden local snapshots created by Time Machine or bloated system cache directories are consuming the required allocation headroom on your primary partition.
• Actionable Fix: Open Terminal and execute the command tmutil listlocalsnapshots / to check for local backups, then delete them or clear your user cache directories to free up the mandatory 20 GB threshold.

Mac Stuck on Apple Logo with Progress Bar During Reboot

• Root Cause: The APFS file system conversion is hanging on corrupted directory structures or failing due to failing sectors on an aging mechanical hard drive.
• Actionable Fix: Force shut down the Mac by holding the power button, boot into Recovery Mode by holding Command-R upon startup, open Disk Utility, run First Aid on your internal volume, and restart the installation process.

Frequently Asked Questions

Can I update directly from OS X Yosemite to High Sierra?

Yes, you can upgrade directly from OS X Yosemite (10.10) or later to macOS High Sierra without needing to install intermediate operating system versions. However, ensure you verify that your legacy 32-bit applications will no longer function, as High Sierra introduces the transition framework toward modern 64-bit software enforcement.

Why is the High Sierra installer saying it cannot be verified?

This error typically occurs because your system date is out of sync or the security certificate on the installer package has lapsed due to age. Adjusting your system date backward via Terminal or downloading a freshly repackaged installer from Apple's official support channels resolves this verification bottleneck.

Is APFS mandatory when updating to High Sierra?

Yes, upgrading your system drive from HFS+ to APFS (Apple File System) happens automatically during the installation process for solid-state drives. Fusion drives and traditional mechanical hard drives may remain on HFS+ depending on the specific hardware configuration detected by the installer script.

How do I create a bootable USB installer for High Sierra?

Download the official installer to your Applications folder, plug in a formatted 9GB+ USB flash drive named Untitled, and execute the createinstallmedia command via the Terminal application. This allows you to perform clean installations across multiple legacy machines without downloading the multi-gigabyte package repeatedly.

Ensure your Mac is properly backed up and connected to a reliable power source before initiating any legacy OS modifications or firmware updates.