1Password supports OS X 10.8.4 (Mountain Lion) and later.
Lion, Tiger, and Leopard versions are also available.
Browser extensions are available for Safari, Firefox, Google Chrome, and Opera.
Windows XP, Windows Vista, Windows 7, or Windows 8 Pro required. Windows RT currently not supported.
Browser extensions provided for many modern browsers
1Password for iOS
1Password for Android
Knox for Mac
Mac OS X 10.6 (Snow Leopard) or above required.
Download Knox 2.0.8 for Mac OS X 10.5 (Leopard) and Mac OS X 10.4 (Tiger).