System Information can find 32-bit apps that are installed on your Mac:
- Choose Apple menu > About This Mac, then click the System Report button.
- Select Legacy Software in the sidebar. All legacy software is 32-bit.
- If you don't see Legacy Software in the sidebar, select Applications in the sidebar, then check the list of apps on the right. The column labeled ”64-Bit (Intel)” shows ”No” for apps that are 32-bit.
When upgrading to macOS Catalina, the installer shows a list of recently used apps that are 32-bit. You can review this list before choosing whether to cancel or continue the installation: