Use Time Machine or an external drive. A clean install will wipe your current data. Boot from USB: Plug the USB into the Mac. Restart the Mac while holding the Option (Alt) ⌥ key.
This guide provides a comprehensive walkthrough for downloading the macOS High Sierra (10.13) DMG file and performing a clean installation. Whether you are reviving an older Mac or need a reliable environment for specific legacy software, High Sierra remains a stable and popular choice. macos high sierra download dmg install
Before downloading, ensure your Mac supports macOS High Sierra. Generally, the following models are compatible: Late 2009 or newer MacBook Air/Pro: Late 2010 or newer iMac: Late 2009 or newer Mac Mini/Pro: Mid 2010 or newer Use Time Machine or an external drive