To implement biometric authentication in a React Native app using Ory, you can utilize the WebAuthn (Web Authentication) standard. However, it's important to note that there are some constraints and limitations when it comes to using WebAuthn with native mobile apps. According to the [Ory documentation on WebAuthn constraints](https://www.ory.sh/docs/kratos/passwordless/passkeys#constraints), WebAuthn is primarily a browser standard and does not work directly in native mobile apps. Additionally, WebAuthn is limited to one domain and doesn't work in a local environment when using CNAME / Ory Proxy. For React Native specifically, there isn't a direct API way to implement the WebAuthn flow. The Android WebView also doesn't support the WebAuthn standard, which further complicates the implementation in native apps. However, Ory does provide a React Native reference implementation that you can use as a starting point. You can find this implementation in the [kratos-selfservice-ui-react-native GitHub repository](https://github.com/ory/kratos-selfservice-ui-react-native). For iOS devices, there is a potential workaround using the Apple SDK. The [Ory documentation on using the Apple SDK for native apps](https://www.ory.sh/docs/kratos/social-signin/apple#using-the-apple-sdk-on-native-apps) provides some guidance on how to implement this. This approach uses the native Apple SDK and doesn't require a browser, resulting in a signed

id_token

on the client side which is then exchanged at Ory for a session token. It's worth noting that as of now, Ory Network doesn't fully support WebAuthn on native devices, but it is on their roadmap for future development. Given these limitations, implementing biometric authentication in a React Native app using Ory might require some custom solutions or workarounds. You may need to explore alternative approaches or wait for future updates from Ory that better support biometric authentication in native mobile apps.