If you are looking to reinstall Catalina or downgrade from a newer OS, finding the correct installer is the first hurdle. Apple hides older installers in plain sight within the App Store.
Apple provides several ways to obtain the 10.15.7 installer, depending on whether you need a full installer or a specific update patch: macOS Catalina - App Store download catalina 10.15.7
(Replace MyVolume with your USB drive’s name.) If you are looking to reinstall Catalina or
// Function to get the current macOS version func getMacOSVersion() -> String let osVersion = ProcessInfo.processInfo.operatingSystemVersion return "macOS \(osVersion.majorVersion).\(osVersion.minorVersion).\(osVersion.patchVersion)" | | Installer quits after download | Check
| Issue | Fix | |-------|-----| | "This copy is damaged" (date error) | Open Terminal and run: date 0101010116 (temporarily sets date back) before launching installer. | | Installer quits after download | Check your Applications folder – it may have saved there already. | | Not enough free space | You need ~20 GB free. Catalina installer is ~8 GB, but installation requires ~12-15 GB more. |