The "companion mode" function was discovered last year in the WhatsApp beta for Android 2.22.15.13 update. Last month, it had been released to all Android users.

Today WhatsApp is rolling out this function to iOS.

Companion Mode allows you to link a secondary mobile device to your WhatsApp account without requiring an active Internet connection on the main device in order to send messages. The chats will automatically sync across both devices.

To link an iPhone as a companion, tap the "link this device" option on the phone number registration screen.

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