Before proceeding, verify that your Mac supports macOS Catalina.

Use the built-in Time Machine tool to create a full system backup to an external drive. This is your safety net if the installation fails.

Upgrading directly from macOS High Sierra (10.13.6) to macOS Catalina (10.15) is possible without intermediate upgrades, provided the target Mac hardware meets Catalina’s system requirements. This report outlines the necessary compatibility checks, data backup procedures, and step-by-step installation instructions. As of 2023–2024, macOS Catalina no longer receives security updates from Apple. Upgrading further to macOS Big Sur (11), Monterey (12), Ventura (13), or Sonoma (14) is strongly recommended if hardware permits.

Typically 45–90 minutes depending on drive speed (HDD vs. SSD).

Your Mac will save the installation files and restart. During the installation process:

If your Mac is older than these models, it is not compatible with Catalina. In that case, you may want to consider staying on High Sierra or upgrading to macOS Mojave (10.14), which supports a broader range of older Macs.

With your preparation complete, it's time to start the upgrade. Since you are upgrading from High Sierra, you will need to go through the Mac App Store.

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Once compatibility is confirmed, the next phase is all about preparation. Skipping these steps is the number one cause of upgrade failures and data loss.

Before jumping in, recognize the crucial change: . If you rely on legacy software like older versions of Microsoft Office or Adobe Creative Suite, they will stop working after this update.

Ensure you have at least 15 GB to 20 GB of available storage . Go to About This Mac > Storage to inspect your current volume.

This is the most critical step. A major OS upgrade carries a small but real risk of data loss or a failed installation that could require erasing your drive. If you have a current backup, you can always restore your system to its previous state.

Select your main hard drive (usually Macintosh HD) and click . Step 3: The Installation Process