WhatsApp Web access is linked to the phone app by scanning a QR code. The user opens WhatsApp Web, displays the code, and uses the mobile app’s linked-devices feature to scan it.
This pairing method avoids typing a long password into the browser. The phone app authenticates the session and authorizes the browser to access the account. WhatsApp Web was released on January 21, 2015, originally supporting Android, BlackBerry, and Windows Phone users.
The QR code is not the same as a barcode, PIN, or NFC tag. QR codes are two-dimensional patterns that can encode data and be read quickly by a camera. WhatsApp uses one as a secure pairing token for the browser session.
Originally, WhatsApp Web depended heavily on the phone remaining connected to the internet. WhatsApp’s multi-device updates, rolled out from 2021 and integrated by default in 2022, reduced that dependence.