If you are currently running Snow Leopard, Lion, Mountain Lion, Mavericks, Yosemite, El Capitan, or Sierra:

This is the simplest method if you have access to it. On any Mac that is from the Late 2009 to Mid-2010 era or newer, you can open the Mac App Store, search for "macOS High Sierra," and click the "Get" or "Download" button. Once downloaded, the installer will launch automatically. If you're not ready to install, just quit the installer, and the file (named Install macOS High Sierra.app ) will remain in your Applications folder.

Expired certificate. Apple stopped signing High Sierra in 2020. Fix: Open Terminal and set the date back during installation:

Apple keeps an "archived" link for High Sierra. This downloads a .pkg file that, when installed, places the "Install macOS High Sierra.app" into your Applications folder. Download macOS High Sierra 10.13.6 from the Mac App Store 2. Utilizing softwareupdate (For Existing Macs)

At least 14.3 GB of available storage space to perform the upgrade

Once you have the installer, you have two options: upgrading your current system or performing a clean install. Method A: Upgrade/Reinstall (Easy)

Before downloading, ensure your Mac hardware officially supports macOS High Sierra. Compatible Mac Models Late 2009 or newer MacBook Air: Late 2010 or newer MacBook Pro: Mid 2010 or newer Mac mini: Mid 2010 or newer iMac: Late 2009 or newer Mac Pro: Mid 2010 or newer Minimum Hardware Requirements Memory: 2 GB of RAM (4 GB or more highly recommended)

Select your USB drive, click , and format it exactly as: Name: HighSierraUSB Format: Mac OS Extended (Journaled) Scheme: GUID Partition Map Open Terminal (Finder > Applications > Utilities). Copy and paste the following command, then hit Enter :

macOS High Sierra is no longer receiving security updates from Apple. This guide is for legacy hardware or specific software compatibility needs. Do not install this on a modern Mac that supports newer OS versions.

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Apple provides a dedicated support page for downloading older versions of macOS.

Released in 2018, macOS High Sierra (version 10.13.6) remains a stable, reliable operating system for older Mac hardware, offering a balance of performance and support for apps that no longer function on modern macOS versions.

Back up all data on the USB drive, as this process completely erases it. Format the USB via Disk Utility Insert your USB flash drive into your Mac. Open (found in Applications > Utilities).

Move the finalized DMG from the temporary folder to your desktop: mv /tmp/HighSierra.dmg ~/Desktop/ Use code with caution.

She exhaled. Official. Good.

Avoid third-party torrent sites or unverified blogs, as their DMG files may contain malware. Always use official Apple channels. Method A: Via the Mac App Store (Recommended)