Only desktop and web are supported, and a few features are missing
WhatsApp has been prepping support for multiple devices for months now — even longer if you consider its semi-functional existing web and desktop implementation as an intrinsic part of the process. The feature started to go live for some users a few days ago, and appears to be spreading widely now. Most beta app users should have it now, and it is making its way to non-beta users too. It’s trivial to set up and, although most functionality is retained, it’s still a little disappointing.
Everything you need to know about WhatsApp’s new multi-device support was written by the awesome team at Android Police.