WeChat Open Platform — Website Login (QR OAuth)
Web-based OAuth 2.0 login that renders a WeChat QR code on third-party websites. End users scan the code in WeChat to authenticate; the website receives a code on its callback URL and exchanges it for a snsapi_login access token plus the user's WeChat OpenID / UnionID. Standard way of adding "Sign in with WeChat" to non-WeChat web properties.