Newer Mac models with Touch ID, Touch Bar, and/or the T2 security chip default to having a secure boot mode that disallows booting the Mac from external startup drives. This security setting is recommended for most users to keep enabled, but some users may wish to turn the feature off, at least temporarily, usually to be able to boot from an external volume, or to be able to perform something like a clean macOS install using a USB boot install disk.

Let’s walk through how you can allow a T2 equipped Mac to boot from external startup drives, whether they’re…