For the best experience, use an SSD (Solid State Drive) rather than an HDD. Look for one with USB-C or Thunderbolt 3/4 connectivity to ensure speeds that match your internal drive.
You need the official installer from Apple. install mac os on external drive
Running your operating system from an external SSD is fast, safe, and doesn't touch your primary data. Here is everything you need to get it running. 1. What You’ll Need Before you start, gather these essentials: For the best experience, use an SSD (Solid
When you see the screen asking where to install macOS, click . For the best experience
APFS (If you are installing a very old OS like High Sierra or older, use Mac OS Extended). Scheme: GUID Partition Map . Click Erase . 3. Step 2: Download the macOS Installer