Glossary
3-D Secure
A protocol that lets a card issuer verify the cardholder during an online payment.
3-D Secure (3DS) adds a step between the merchant and the issuer in which the issuer can check that the person paying is the cardholder. The check may happen silently, using device and transaction data, or as a challenge such as a one-time code or a banking-app approval.
The current version, 3DS2, shares far more data with the issuer than the original protocol, so most transactions can be approved without a challenge. When authentication succeeds, liability for certain fraud chargebacks usually shifts from the merchant to the issuer.