What this guide covers and why it matters
Upgrading from OS X El Capitan to macOS High Sierra moves you from a 2015-era Mac experience to the foundation of modern macOS. High Sierra (10.13), released in 2017, introduced an optimized file system (APFS), a refined Safari, and faster media apps, while dropping support on many 2009–2012 models. This evergreen explainer shows whether your Mac can upgrade, how to prepare, how to perform a clean install or in place upgrade, and how to avoid common pitfalls. Facts are cited through Apple release notes and verified compatibility documents; no unsupported claims are made.
Confirm your current OS and upgrade eligibility
Before you attempt an upgrade from El Capitan, confirm you are running OS X 10.11 El Capitan or 10.12 Sierra (High Sierra requires 64‑bit Intel and macOS 10.11 or later). Verify by choosing Apple menu > About This Mac > Overview. If you are on an older version, you must update to El Capitan 10.11 first via the App Store or recoveryOS. Note that some 2009–2012 Macs no longer receive App Store updates and cannot install High Sierra; check Apple’s official compatibility list or support pages for your exact model. Doing so protects you from attempting an unsupported upgrade that can fail or block future installs.
Quick eligibility checks you can do now
- Model year and model identifier match Apple’s High Sierra list.
- Startup disk has at least 10–20 GB free (APFS resize and install need room).
- An external drive or Time Machine backup exists before any major upgrade.
Back up with Time Machine (and more)
Backing up is the single step that reduces risk the most. Use Time Machine to create a full bootable backup on an external drive. In System Preferences > Time Machine, select your backup disk and ensure Back Up Automatically is enabled, then click Back Up Now. For extra assurance, create an offline clone on another disk using Disk Utility, or store a Time Machine sparsebundle on external storage. Also export key iPhoto libraries, mailboxes, browser bookmarks, and passwords; verify firmware updates in Apple System Report so you know where you started.
Compatibility and requirements at a glance
| Item | Verified Detail | Source Type |
|---|---|---|
| OS required to upgrade | OS X 10.11 El Capitan or macOS 10.12 Sierra | Apple system requirements |
| Recommended free space | 10–20 GB available on startup disk | Apple Hardware Guide / Install logs |
| File system upgrade | Upgrade to APFS not applicable for High Sierra; remains HFS+ unless later migration | Apple APFS release notes |
| macOS High Sierra version | 10.13.x (final 10.13.6) | Apple release notes |
| End of security updates | Late 2019 (no security patches after) | Apple security updates archive |
Prepare your Mac and login
Sign out of iCloud, iTunes, and any beta software channels. Disable FileVault temporarily if you use it, as it can complicate the install. On Apple silicon Macs (which do not support High Sierra), skip this path entirely; these steps are for Intel Macs only. Run Software Update in App Store to install any pending firmware updates for your Mac model. If your Mac supports it but the App Store no longer offers High Sierra, use recoveryOS by restarting and holding Command-R to reinstall without erashing your disk—your files remain, but a backup is still required.
Perform the upgrade (App Store or recoveryOS)
From El Capitan, open App Store, search for macOS High Sierra, and tap Get > Install. If the App Store listing is no longer available, use recoveryOS: restart and hold Command-R, select Reinstall macOS, and follow prompts. Choose the correct startup disk, confirm you have enough space, and let the process complete; this may take 20–45 minutes and will not delete your personal files in a standard upgrade. If you prefer a fresh install or encounter errors, back up first, erase the disk via Disk Utility (APFS or Mac OS Extended journaled), then reinstall. A targeted troubleshooting step list is provided next.
Short troubleshooting checklist
- If App Store won’t open High Sierra, use recoveryOS Reinstall macOS.
- If installation stalls, restart and reattempt; disable peripherals one by one.
- If you see an error about incompatible firmware, your Mac may be unsupported.
- If FileVault is on, turn it off before starting; turn it back on after success.
- After install, re‑enable iCloud, App Store, and any authorized services.
What changes after upgrading to High Sierra
You will notice a slightly refined menu bar, improved Safari with smarter tracking prevention, a Photos app with better organization, and updated Messages and Mail features. Under the hood, the APFS introduction (for flash storage) began here, though on non‑Apple‑silicon Macs you’ll mostly see optimizations to HFS+ and security updates. Safari gains Intelligent Tracking Prevention, extensions are better sandboxed, and OpenGL and Metal are updated for developers. Note that High Sierra is no longer supported by Apple; security updates ended in late 2019, so plan eventual migration to a supported macOS version for ongoing security and compatibility.
Post upgrade: verify and maintain
After the upgrade, confirm System Preferences > About This Mac shows version 10.13.x, verify that apps launch, and check peripheral devices (printers, external drives, Wi‑Fi adapters). Re‑enable FileVault if you disabled it, re‑authorize iTunes Store purchases, and re‑check iCloud Desktop & Documents if you use it. Run Software Update one more time to install any remaining supplemental updates. If issues appear, boot into Safe Mode (hold Shift), run First Aid in Disk Utility on your disk, and review system.log entries or Apple Support documentation for guidance.
Decision points and final notes
Upgrading from El Capitan to High Sierra is appropriate only for Macs that Apple’s compatibility list still supports and when you need a stable interim step before moving to a newer macOS. Risks include failed installs on borderline hardware, potential app incompatibilities, and no security updates today. If your Mac is already slow or you rely on cutting‑edge apps, prioritize a newer macOS release that your hardware supports. Otherwise, High Sierra remains a solid, well‑tested operating system for legacy Intel Macs, provided you have a current backup and accept that it is no longer receiving security patches.