> ## Documentation Index
> Fetch the complete documentation index at: https://auth0.com/llms.txt
> Use this file to discover all available pages before exploring further.

> How to implement Touch ID / Face ID authentication with Auth0.swift.

# Auth0.swift: Touch ID / Face ID Authentication

export const AuthCodeBlock = ({filename, icon, language, highlight, children}) => {
  const [displayText, setDisplayText] = useState(children);
  const [copyText, setCopyText] = useState(children);
  const wrapperRef = React.useRef(null);
  useEffect(() => {
    let unsubscribe = null;
    function init() {
      if (!window.autorun || !window.rootStore) {
        return;
      }
      unsubscribe = window.autorun(() => {
        let processedChildrenForDisplay = children;
        let processedChildrenForCopy = children;
        for (const [key, value] of window.rootStore.variableStore.values.entries()) {
          const escapedKey = key.replaceAll(/[.*+?^${}()|[\]\\]/g, (String.raw)`\$&`);
          let displayValue = value;
          if (key === "{yourClientSecret}" && value !== "{yourClientSecret}") {
            displayValue = value.substring(0, 3) + "*****MASKED*****";
          }
          processedChildrenForDisplay = processedChildrenForDisplay.replaceAll(new RegExp(escapedKey, "g"), displayValue);
          processedChildrenForCopy = processedChildrenForCopy.replaceAll(new RegExp(escapedKey, "g"), value);
        }
        setDisplayText(processedChildrenForDisplay);
        setCopyText(processedChildrenForCopy);
      });
    }
    if (window.rootStore) {
      init();
    } else {
      window.addEventListener("adu:storeReady", init);
    }
    return () => {
      window.removeEventListener("adu:storeReady", init);
      unsubscribe?.();
    };
  }, [children]);
  useEffect(() => {
    if (!wrapperRef.current) return;
    const originalWriteText = navigator.clipboard.writeText.bind(navigator.clipboard);
    let isOverriding = false;
    const handleClick = e => {
      const button = e.target.closest('[data-testid="copy-code-button"]');
      if (!button || !wrapperRef.current.contains(button)) return;
      isOverriding = true;
      navigator.clipboard.writeText = text => {
        if (isOverriding) {
          isOverriding = false;
          navigator.clipboard.writeText = originalWriteText;
          return originalWriteText(copyText);
        }
        return originalWriteText(text);
      };
      setTimeout(() => {
        if (isOverriding) {
          isOverriding = false;
          navigator.clipboard.writeText = originalWriteText;
        }
      }, 100);
    };
    const wrapper = wrapperRef.current;
    wrapper.addEventListener('click', handleClick, true);
    return () => {
      wrapper.removeEventListener('click', handleClick, true);
      if (navigator.clipboard.writeText !== originalWriteText) {
        navigator.clipboard.writeText = originalWriteText;
      }
    };
  }, [copyText]);
  return <div ref={wrapperRef}>
      <CodeBlock filename={filename} icon={icon} language={language} lines highlight={highlight}>
        {displayText}
      </CodeBlock>
    </div>;
};

Here's the scenario: After user authentication, you want to store the user's credentials and use them as long as they are valid. Once they expire, you would want to renew them using the `refreshToken` in order to avoid presenting the login page again. Rather than doing this automatically, you require the user to validate with their fingerprint or face.

You will be using the [Credentials Manager](https://github.com/auth0/Auth0.swift/blob/master/Auth0/CredentialsManager.swift) utility in [Auth0.swift](https://github.com/auth0/Auth0.swift/) to streamline the management of user credentials and perform biometric authentication.

## Getting Started

First, import the `Auth0` module:

`import Auth0`

### Credentials Manager

Before retrieving credentials, you can also engage the biometric authentication (Face ID or Touch ID) supported by your iOS device.

Begin by setting up the Credentials Manager. Then enable biometrics. You can also pass in a title to show in the prompt.

```swift lines theme={null}
let credentialsManager = CredentialsManager(authentication: Auth0.authentication())
credentialsManager.enableBiometrics(withTitle: "Touch ID / Face ID Login")
```

We strongly recommend that you add the [NSFaceIDUsageDescription](https://developer.apple.com/library/archive/documentation/General/Reference/InfoPlistKeyReference/Articles/CocoaKeys.html#//apple_ref/doc/uid/TP40009251-SW75) setting to your project's `Info.plist` to display a reason for using Face ID. In some cases, if you do not provide a description string and the user attempts Face ID authentication, the user's attempt may fail.

```xml lines theme={null}
...
<key>NSFaceIDUsageDescription</key>
<string>Reason why we use Face ID here</string>
...
```

### Login

Present the <Tooltip tip="Universal Login: Your application redirects to Universal Login, hosted on Auth0's Authorization Server, to verify a user's identity." cta="View Glossary" href="/docs/glossary?term=Universal+Login">Universal Login</Tooltip> page and, upon successful authentication, pass the credentials to the Credentials Manager.

export const codeExample = `Auth0
    .webAuth()
    .scope("openid profile offline_access")
    .audience("https://{yourDomain}/userinfo")
    .start {
        switch $0 {
        case .failure(let error):
            // Handle error
        case .success(let credentials):
            // Store credentials securely with the Credentials Manager
            credentialsManager.store(credentials: credentials)
        }
}`;

<AuthCodeBlock children={codeExample} language="swift" />

### Renew User Credentials

When you need to renew the user's credentials, you can call the `credentials` method from the Credentials Manager.

```swift lines theme={null}
credentialsManager.credentials { error, credentials in
    guard error == nil, let credentials = credentials else {
        // Handle error
        // Fallback to login screen
    }
    // Continue routing the user as authentication was successful
}
```

There is no need manually store the new credentials as this is handled by the Credentials Manager during the renewal.

## Next Steps

You can download a sample project and follow the instructions in the iOS quickstart section on [Touch ID / Face ID in iOS](/docs/quickstart/native/ios-swift).