> ## Documentation Index
> Fetch the complete documentation index at: https://circle-devdocs-test-ai-codegen-component.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# Passkey

Circle's **Passkey** enables the integration of secure smart contract
functionality through the **WebAuthn** standard. By using the Passkey as a
signer, it simplifies user onboarding and enhances the signing experience.
Passkey also offers a secure and seamless way to manage private keys, allowing
your users to interact with smart contracts safely and efficiently.

## Passkeys Overview

Passkeys simplify private key management in Web3, improving user experience.
Users no longer need to handle private keys directly or worry about losing their
12-word seed phrase, which could result in lost funds.

### What is a Passkey?

A passkey is a cryptographic key pair generated and **securely stored on user
devices**, such as laptops, phones, or password managers like 1Password. Unlike
passwords, passkeys cannot be shared and are resistant to phishing and breaches.

<Note>
  Passkey adoption is growing, with Apple and Google promoting this standard. Passkeys are now available on many devices, including:

  * **Apple**: iPhones, iPads, MacBooks
  * **Android**: Phones and tablets
  * **Browsers**: Chrome, Edge, Firefox (on Windows, Mac, and Android)
  * **FIDO2 security keys**: YubiKey and similar devices

  See the full
  [passkey support matrix](https://passkeys.dev/device-support/#matrix) for device
  and platform compatibility across various operating systems and browsers.
</Note>

### Benefits of Passkeys

* **Faster Registration and Login**. Users can register and log in using
  biometric authentication, such as Face ID or fingerprints.
* **Ease of Use**. Passkeys sync with password managers like iCloud Keychain,
  Google Password Manager, or 1Password, allowing seamless access across devices
  within the same ecosystem.
* **Cross-Device Usage**. Passkeys can be used across different ecosystems via
  **Bluetooth**. For example, users can sign in on another device by scanning a
  QR code with their phone, as long as the phone is near the laptop and the user
  approves the sign-in on their phone.\
  **Note:** If you sign in on the same device where the passkey was created, the
  device will prompt you to authenticate using biometrics — no Bluetooth
  required. For more details, see
  [this guide](https://blog.1password.com/passkeys-faqs/#do-you-need-a-bluetooth-connection-to-use-a-passkey).

## Passkey Implementation

Circle’s **Passkey** feature is built using **Smart Contract Passkey** alongside
**webAuthnAccount**. A dedicated **Passkey Server** is implemented to enable
secure registration and authentication processes through the **WebAuthn**
standard.

* **Smart Contract Passkey**. A digital key that authorizes blockchain
  transactions, ensuring only authorized users can execute actions.
* **WebAuthnAccount**. WebAuthn is a web standard for secure authentication
  using public key cryptography instead of passwords. WebAuthnAccount connects
  to Circle’s Passkey Server to retrieve passkeys registration and login
  credentials, enabling the generation of passkeys and performing signing
  operations.

Passkeys use the **secp256r1** curve for generating signatures. When invoking
**webAuthnAccount**, the signing methods return both the signature and the
associated **WebAuthn** data.

## Passkey Backup and Recovery

As passkeys replace traditional private keys in Web3 authentication, having a
reliable backup and recovery strategy becomes essential. This section explains
how passkeys are synchronized across user devices and what fallback options
Circle provides in case users lose access to their original passkey, including
support for recovery keys with secure, self-custodial properties.

Passkeys are natively synchronized across user devices via secure cloud storage
services like **Apple iCloud Keychain** or
[Google Password Manager](https://developers.google.com/identity/passkeys/supported-environments),
ensuring convenience and accessibility. However, **device-bound passkeys** (for
example, YubiKey) do not support synchronization, as they remain exclusive to
the device where they were created. This offers higher security but less
convenience:

* **Apple iCloud Keychain**. Syncs passkeys across Apple devices as long as the
  user is signed in with their Apple ID.
* **Google Password Manager**. Enabled by default as a passkey provider on
  Android, and accessible in Chrome and other supported browsers.

Despite these measures, users may accidentally erase their passkey setup or lose
a hardware security key. To address this risk, Circle provides an additional
recovery method to ensure continued account access. For more details and sample
code, visit the
[How to set up passkey recovery](/wallets/modular/recover-passkey) guide.

<Note>
  **Key Benefits:**

  * **Self-Custodial**: No central authority required for recovery
  * **Equivalent Permissions**: Recovery keys have the same permissions as
    passkeys at the contract level
  * **Standard Compatibility**: Recovery keys use standard ECDSA signatures,
    compatible with Ethereum tooling
  * **Multiple Recovery Keys**: Support for registering multiple recovery keys
    for added flexibility and security
</Note>

<Warning>
  **Caution:**

  The passkey and any recovery methods that users set up are the only ways to
  access their wallets. Neither Circle nor developers can possibly recover user
  wallets under any circumstances.
</Warning>

## How to Use Passkey

Explore the following resources to integrate the Passkey functionality into your
Web3 applications:

* [Modular Wallets Quickstart](/wallets/modular/create-a-wallet-and-send-gasless-txn)
  showcases how your app users can authenticate using a passkey.
* [Sample App](https://github.com/circlefin/modularwallets-web-sdk/tree/master/examples/circle-smart-account)
  in the [Modular Wallet Web SDK](/wallets/modular/web-sdk) (and the
  [Android](/wallets/modular/android-sdk) and [iOS](/wallets/modular/ios-sdk)
  SDKs) provide implementation examples.