Choose a disk format by where the drive must work and what it will store. A disk for a Mac application library has different requirements from a drive used to exchange ordinary files with Windows computers.

Start with the intended use

Apple documents APFS support in macOS 10.13 and later. APFS offers Mac features including encrypted and case-sensitive variants. For a Mac-only working disk, check whether the application you intend to use recommends APFS or another specific format.

For ordinary file exchange with Windows, Apple's Disk Utility guide identifies exFAT as a Windows-compatible choice. That compatibility does not mean every Mac library, backup tool, television or camera supports using an exFAT drive for its own storage. Check the actual destination device or application.

Choose case-sensitive APFS only when the workflow requires it. It treats names such as “Project” and “PROJECT” as different. An unnecessary change in that behaviour can create confusion for applications and collaborators expecting ordinary Mac naming conventions.

Protect the current contents before changing anything

Inspect the drive in Finder and identify its capacity and existing files. If it contains the only copy of anything important, do not proceed with an erase or reformat. Copy required material to another independent destination and verify that it opens.

In Disk Utility, carefully distinguish the external device from the Mac's internal storage and from individual volumes. Stop when the selection or consequences are unclear. Formatting is a setup operation, not a way to retrieve files from a disk that has suddenly become unreadable.

After preparing an empty drive, test the real workload. Copy a disposable file, open it, safely eject the drive and reconnect it. For cross-platform use, repeat on the other computer. For a library or backup application, complete its own setup and verification before moving the only working copy.

Source: Apple's Disk Utility format reference.

For help with your Mac, contact AEPC in East Auckland or call 027 908 8880 to discuss your requirements.