Downloading is still entirely possible through a combination of Apple’s legacy support page, Terminal conversions, and trusted archiving sites. The key is to prioritize security: stick with Apple’s CDN when possible, verify checksums, and never run unsigned installer packages from random forums.
Alternatively, search for trusted third-party repositories that offer the direct InstallMacOSX.dmg file from Apple's servers. System Requirements for High Sierra Before downloading, ensure your Mac supports macOS 10.13: MacBook Pro (Mid 2010 or newer) MacBook Air (Late 2010 or newer) iMac (Late 2009 or newer) Mac Mini (Mid 2010 or newer) Mac Pro (Mid 2010 or newer) RAM: At least 2GB (4GB recommended) Storage: At least 15GB of free space. How to Install macOS High Sierra 10.13.6 download macos high sierra 10.13.6 dmg mac
Ensure that the installer app is fully downloaded and sitting directly in your main folder. If you renamed the installer or left it in your Downloads folder, the command will fail. Downloading is still entirely possible through a combination