WhatsApp is rolling out login on multiple smartphones at the same time. Mark Zuckerberg announced the rollout on Facebook and Instagram.
“Starting today, you can log into the same WhatsApp account on up to four phones,” he said.

The feature is rolling out to all users within the coming weeks.Currently, users could only use a WhatsApp account on one smartphone and multiple companion desktop devices (laptops, etc).
With the new feature, users can now enjoy synced messages across devices including other smartphones even if one device is switched off.
