Typically 45–90 minutes depending on drive speed (HDD vs. SSD).
Below is a detailed, safe walkthrough to get you from 10.13.6 to 10.15. how to update macos high sierra 10.13.6 to 10.15
For users still running macOS High Sierra (10.13.6), moving to macOS Catalina (10.15) represents a significant architectural shift. This is not a minor patch but a complete operating system upgrade that changes how your Mac handles apps, media, and security. Typically 45–90 minutes depending on drive speed (HDD vs
Delete the installer and redownload using the official App Store link. Or in Terminal, run sudo spctl --master-disable before launching the installer. how to update macos high sierra 10.13.6 to 10.15