General term for a keychain, a ring or chain for holding keys. Often used interchangeably with キーホルダー, though キーホルダー may emphasize the decorative holder aspect.
See also: キーホルダー
I bought a new keychain.
That keychain has a small light attached.
Keychain (Apple password manager)
Computing term referring specifically to Apple's Keychain password management system in macOS and iOS.
Save the password in the Mac's Keychain.