# Transaction Authentication
source: https://developer.mastercard.com/mastercard-checkout-solutions/documentation/use-cases/token-authentication-service/index.md

Mastercard offers Token Authentication Service (TAS) for seamless cardholder authentication using payment passkeys.

Mastercard TAS allows participating Integrators to perform cardholder authentication using device binding, biometric authentication, or alternative authentication methods during transactions in Secure Card on File and Click to Pay.

For more information, refer to the [TAS Product Guide - TO BE UPDATED](https://techdocs.mastercard.com/).
Note: Contact a [Mastercard representative](https://developer.mastercard.com/mastercard-checkout-solutions/documentation/support/index.md#get-help) to check the regional availability for TAS.

## Products supporting Authentication using TAS {#products-supporting-authentication-using-tas}

### Click to Pay {#click-to-pay}

Merchants can request transaction authentication with payment passkeys during checkout for new and returning users.


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[View Tutorial](https://developer.mastercard.com/mastercard-checkout-solutions/tutorial/authentication_c2p/index.md)

### Secure Card on File {#secure-card-on-file}

Merchants can request transaction authentication with payment passkeys during checkout.


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[View Tutorial](https://developer.mastercard.com/mastercard-checkout-solutions/tutorial/authentication_scof/index.md)