WhatsApp is working on the feature that it allows you to use the same account across different devices at the same time. The messaging platform has worked on a single device all this time and reports have it that this new feature is being worked on in parts. As and when the feature rolls out, users should be able to use WhatsApp across four different devices at the same time. WhatsApp is working to create an interface on the Android app and on WhatsApp for iOS.
When a user wants to use WhatsApp on a second device, there is that issue of copying the chat history. For this, WhatsApp will require a WiFi connection since it may use a large amount of your data plan. WABetaInfo reports that WhatsApp Desktop was used for the test here but it will work on a second mobile device too. It is possible that WhatsApp will allow other mobile devices to be connected to your main device slightly later than WhatsApp desktop. Using this feature, Internet connection on your device will not be needed to WhatsApp Desktop.
Once WhatsApp has copied the chat history to the second device, it will be finally possible to use your account from it. Any message will be delivered to all your family devices, so that your chat history is going to be synced across the platforms and when you use or remove a device, your encryption key changes. When your encryption key changes, all active chats will be notified, if your Security Notifications are on.
Support between Android and iOS devices is not confirmed yet, but it might be something WhatsApp is going to bring in too. WhatsApp was working on converting the iOS database to the one that’s compatible with the Android format previously. This feature is under development and it will be available in future.