Creating a bootable USB installer for macOS High Sierra is useful when you need to install the OS on an unsupported Mac, perform a clean reinstall, or run diagnostics. This process prepares a USB drive containing the complete macOS High Sierra installer so you can boot from it and access Disk Utility, reinstall macOS, or erase the startup disk safely. It also makes it easier to set up multiple Macs or recover a system that fails to boot normally. The following explains compatibility, step-by-step methods, and verification checks.
Compatibility and Prerequisites
Confirm that your Mac supports macOS High Sierra (10.13) before preparing the USB. Many 2012 and later Macs are compatible, while some older models are not. This determines whether the steps below are applicable to your hardware.
macOS High Sierra Compatibility Table
| Attribute | Verified Detail | Source Type |
|---|---|---|
| Minimum OS X/macOS version to install | OS X Mountain Lion (10.8.2) or later for software updates; some models require OS X Yosemite (10.10) to download from App Store | Apple System Requirements |
| Recommended USB drive capacity | 8 GB or larger; 16 GB recommended for installer and extra files | Best Practice Guidance |
| macOS High Sierra version | 10.13.6 is the last update; still available from Apple via Downloads or Recovery when supported | Apple Release Notes |
| Drive preparation method in Apple silicon Macs | Use Disk Utility and Recovery to create a bootable USB; Startup Security Utility allows external boot | Apple Documentation |
| Drive preparation method in Intel Macs | Disk Utility to erase and create GUID Partition Map; Terminal to create bootable install media | Apple Support Documentation |
Preparing the USB Drive
Formatting the USB drive correctly is essential for it to be recognized as a bootable macOS installer. Use a single, GUID Partition Map, a single Mac OS Extended (Journaled) volume named install, and ensure sufficient space.
Format Checklist
- Use a USB 2.0 or 3.0 drive with at least 8 GB, ideally 16 GB.
- Back up all data on the drive, because formatting erases everything.
- On macOS, open Disk Utility, select the drive (not a volume), click Erase, choose GUID Partition Map, format APFS or Mac OS Extended (Journaled), and name it install.
- Verify that the drive appears in Disk Utility before proceeding.
Download macOS High Sierra
You must obtain the macOS High Sierra installer from the App Store or directly from Apple when App Store access is not available. Confirm the build version to ensure completeness. Note that App Store links for older macOS versions may be region-specific or temporarily unavailable.
Verify Download Integrity
After downloading, verify the installer package name and approximate size to reduce corruption issues. Typical installer names include Install macOS High Sierra or similar, and a complete download should match expected sizes reported by Apple for the version.
Using Terminal to Create Bootable USB
The createinstallmedia command in Terminal copies the installer to the USB and makes it bootable. This method works reliably on Intel-based Macs and requires precise disk identifiers. Always double-check the identifier to avoid erasing the wrong drive.
Terminal Steps (Intel Mac)
- Insert the formatted USB drive named install.
- Open Terminal from Applications > Utilities.
- Run diskutil list to identify the USB drive identifier, typically disk2 or disk3.
- Unmount the drive with diskutil unmountDisk diskX, replacing X with the correct identifier.
- Run the sudo /Applications/Install\ macOS\ High\ Sierra.app/Contents/Resources/createinstallmedia --volume /Volumes/install --nointeraction and confirm when prompted.
- Wait until the terminal reports Copy complete. Done, then eject the drive safely.
Disk Utility Method (Apple Silicon Mac)
Apple silicon Macs require a slightly different workflow using Disk Utility and Recovery. Use Startup Security Utility to allow external boot if needed, create an external installer, then boot from the USB.
Apple Silicon Steps
- Insert the formatted USB drive named install.
- Restart and hold power button until options appear, then select Options and Continue into Recovery.
- Open Disk Utility, select the USB drive, click Erase with GUID Partition Map and APFS or Mac OS Extended, name it install, then Eject.
- Return to Recovery, select Startup Disk, choose the USB drive, and click Continue. If not listed, use Startup Security Utility to set external boot to allow booting from USB.
- When the installer starts, select your target disk to install macOS High Sierra.
Booting from the USB
After preparing the USB, restart your Mac and hold the appropriate key to select the USB. On Intel Macs, use Option (Alt) at startup. On Apple silicon, hold the power button and select the USB from the boot options to begin installation.
Boot Selector Comparison
| Attribute | Intel Macs | Apple Silicon Macs |
|---|---|---|
| Key to press at startup | Option (Alt) | Power button until options appear |
| Select USB name | Windows installer or macOS install | External install of macOS High Sierra |
| Security settings | Startup Security Utility in Recovery | Startup Security Utility in Recovery |
Troubleshooting and Considerations
If the USB is not recognized, recheck the partition scheme and volume name, verify Terminal disk identifiers, and ensure the macOS High Sierra installer matches the intended OS version. Internet Recovery may not provide High Sierra directly if it is no longer offered in standard channels; in such cases, a previously downloaded installer or alternative download methods may be required.
Common Issues Checklist
- Incorrect disk identifier in Terminal can lead to data loss; always confirm with diskutil list.
- Firmware password may block booting from external media; temporarily disable if necessary.
- App Store version unavailable; use an existing installer or official recovery methods.
- USB not booting; recreate the installer and verify partition map GUID and volume name.
Conclusion
Creating a bootable USB for macOS High Sierra is straightforward when you follow verified steps for your Mac architecture. Properly formatting the drive, confirming download integrity, and using the correct commands or Recovery options ensures a reliable bootable installer. This method supports clean installs, multi-Mac setups, and troubleshooting when standard startup is unavailable.