External drives · Passwords and encryption
How do I remove the password or encryption from an external drive?
Short answer: Control-click the drive in Finder, choose Decrypt and enter the password; macOS removes the encryption in the background while your files stay put. If Decrypt isn't offered, copy files off, erase the drive unencrypted, and copy them back.
In Finder, Control-click the drive and choose Decrypt "drive name", then enter its password. macOS decrypts it in the background while you keep using it; your files stay where they are. Leave the drive connected until it finishes — large drives take a while.
If Decrypt isn't offered, the drive's format may not support it in Finder; in that case copy your files off, erase the drive without encryption in Disk Utility, and copy them back.
Think twice before decrypting a drive you carry around: anyone who finds it can then read it. Keeping it encrypted and letting your keychain remember the password is usually the better trade.