Understanding QR Code Login: Principles, Token Authentication, and Implementation Steps

QR codes appear in many daily scenarios such as payments, system logins, and app downloads; understanding their underlying technology helps developers choose appropriate solutions and helps non‑technical users recognize legitimate codes.

Login authentication fundamentally involves two actions: telling the system who you are and proving that identity. Traditional methods use a username/password or a phone‑number/verification‑code pair.

QR‑code login leverages a token‑based authentication mechanism. After a user initially logs in on a mobile device, the client receives a token that represents the account and device. The token, together with device information, is stored on the server and used for subsequent API calls.

When a PC or web client wants to log in via QR code, it requests the server to generate a unique QR‑code ID and binds this ID to the PC’s device information. The server returns the ID, which the client encodes into a QR code displayed to the user.

The user scans the QR code with a logged‑in mobile app. The app sends the scanned QR‑code ID and the user’s identity to the server, which binds the ID to the account and issues a temporary one‑time token.

The mobile app then prompts the user to confirm the login. Upon confirmation, the server generates a permanent login token for the PC, which the PC retrieves through its polling mechanism and uses for authenticated API access.

Because the token never contains the password and is tied to device‑specific information, the approach is secure: even if the token is intercepted, it cannot be used from another device.

Overall, QR‑code login combines QR‑code generation, token authentication, and stateful polling to achieve a seamless and secure cross‑device login experience.

Example token object used in the authentication flow:

const token = {<br/>  accountid: '账号ID',<br/>  deviceid: '登录的设备ID',<br/>  deviceType: '设备类型，如 iso,android,pc......',<br/>}