Review: Upgrading macOS High Sierra 10.13.6 to macOS 10.15 (Catalina)

Summary

Report: Updating macOS High Sierra (10.13.6) to macOS Catalina (10.15)

The install may take 30–90 minutes. Do not close the lid or turn off your Mac.

Step 2: Before You Begin – Critical Preparations

Upgrading across three major versions (10.13 → 10.15) carries risks. Follow these steps strictly.