What is full disk encryption and when should it be used?

Full disk encryption, or FDE, encrypts the entire contents of a storage device so that data is unreadable without the correct authentication credentials at boot time. BitLocker for Windows and FileVault for macOS are common implementations. FDE protects data at rest if a device is lost, stolen, or decommissioned, making the data inaccessible to anyone without the decryption key. It should be used on all laptops, mobile devices, and removable media that may contain sensitive data.