It’s a bit harder to find a Thunderbolt powered SSD, and unfortunately they are a lot more expensive. San Disk USB Type-C drive with 256GB for £30.93 (RRP £59.99). You can get hold of a USB flash stick pretty cheaply, such as this It’s also worth investing in a USB C or Thunderbolt 3 drive as this will offer the fastest connection. Make sure that you opt for flash storage because Apple’s APFS (Apple file system) is optimized for SSD and the computer will be sluggish if you attempt to boot from a hard drive. If you want to run macOS on an external drive you will need a few things including a drive with a good amount of storage available. Run macOS on the external drive by pressing Alt/Option at start up on an Intel-powered Mac, or pressing and holding the on switch on an M1 Mac.Get the macOS install files – we’ll show you how.
Prepare the external drive for the installation using Disk Utility.