This week, WhatsApp announced Windows and OS X versions of its popular messaging app. Until now, desktop users have had to use WhatsApp through a Web browser. Like the Web version, WhatsApp's desktop apps mirror the messages on your phone.
The desktop apps may offer better security than the browser client, giving you and WhatsApp more control over the bits getting sent back and forth. That's important, because WhatsApp now advertises end-to-end encryption on all platforms.
End-to-end encryption means that only the sender and receiver can see the messages. With most other messaging apps, the service gets a copy of your encryption keys, meaning a rogue employee could read your messages without consent or notification, or hand the keys over to law enforcement.
The WhatsApp download page says that Windows users must have Windows 8 or higher, but we had no trouble getting the desktop client to run on Windows 7. Mac users need OS X 10.9 or higher.