Visit the official macOS Catalina page on the Mac App Store.

Surprisingly, Catalina remains relevant. Apple recently released security updates (Catalina Security Update 2026-001) to extend the life of essential services like iMessage and FaceTime on older hardware. This makes it a great "legacy" OS for machines that can't run Big Sur or Monterey. Summary Checklist

The safest way to get the installer is through the official Apple Support download links . Even if Catalina doesn't show up in a standard App Store search, Apple provides direct database links for older versions. Visit the macOS download page on your Mac.

This guide explains how to securely download the full installer and create your own bootable DMG file using official Apple channels.

For users who specifically require a DMG or ISO (often used for VirtualBox or VMware setups), the standard practice is to create one from the official App Store installer. This is a technical process involving the Terminal application. The general steps include:

Apple still hosts the official Catalina installer on its support site.

If the App Store method fails, try Terminal: