The Desktop Web Client will run only on Chrome Browser and is a direct clone of the phone application and will require access to the Internet (phone and desktop).
[blockquote cite=”Jan Koum, CEO and Co-Founder of WhatsApp”]The latest update of the Phone App adds the WhatsApp Web options in the Menu. To use the App via desktop users will have to Scan the QR Code. Once done, all the Contacts will be synced there and will be greeted with a larger phone like interface.[/blockquote]
Jan Koum, CEO and Co-Founder of WhatsApp has explained it at its post on Facebook. Sadly, there iOS users will be missed out due to limitations on Apple Platform.