The download file is roughly 8 GB. Once completed, the installer will automatically launch on your screen, titled Install macOS Catalina . Click and follow the onscreen prompts.
Open your essential applications to check if they require updates to work in 64-bit mode.
Once the installer downloads, it will launch automatically. Follow the prompts. Note that your Mac will restart several times. If you are upgrading from High Sierra on a spinning Hard Drive (HDD) to an SSD file system (APFS), the installation process may take significantly longer than usual.
I can provide custom terminal commands or workarounds to ensure your upgrade goes smoothly. Share public link how to update macos high sierra 10136 to 1015
Total installation time: (depending on drive speed: SSD = ~45 min, HDD = 1.5+ hours).
Check the column. Any app listed as "No" will stop working after upgrading to 10.15. Update or find alternatives for these apps prior to upgrading. Step-by-Step Installation Guide
You need a minimum of 12.5 GB of available storage if upgrading from High Sierra. Apple recommends keeping up to 20 GB free to prevent installation stalls. Memory: At least 4 GB of RAM is required. The download file is roughly 8 GB
Catalina completely removes support for 32-bit applications. High Sierra runs them fine; Catalina will refuse to open them.
Select your primary hard drive (usually Macintosh HD) as the destination.
Because macOS Catalina is an older operating system, it will no longer show up automatically as an available update in your High Sierra Software Update preference pane. You must pull it directly from the Mac App Store via a dedicated link. Open your essential applications to check if they
Upgrading your Mac from macOS High Sierra (10.13.6) to macOS Catalina (10.15) introduces a modernized operating system. This jump replaces 32-bit app support with a strict 64-bit architecture, splits iTunes into dedicated media apps, and adds enhanced security features. Because this is a major system transition rather than a minor patch, proper preparation and execution are critical to avoid data loss. Phase 1: Verify Hardware Compatibility
Major updates can occasionally look frozen. Give it up to two hours. If it remains completely frozen for hours, press and hold the power button to force a shutdown, wait 10 seconds, and turn it back on to see if it resumes.
Because of the version gap, you cannot simply click "Update" in System Preferences. You need the full installer. Open the App Store on your Mac. Search for "macOS Catalina".