3DS2 AReq / ARes Builder & Decoder

Build and decode EMV 3-D Secure (3DS2) authentication messages. Construct an AReq from a form, or paste any AReq/ARes JSON to get a field-by-field explanation with transStatus, ECI, and reason-code lookups — all in your browser.

Follows EMV 3-D Secure Protocol and Core Functionsv2.3.1.1·verified Sep 2026— v2.4 draft with EMVCo Associates