Introduction

1. About API V3

To provide merchants with a simple, consistent and easy-to-use development experience while ensuring payment security, we have launched the latest WeChat Pay API V3.

Compared with the previous WeChat Pay API, it mainly features the following differences:

• Unified REST design style

• Uses JSON instead of XML as the format of data exchange

• Uses the digital signature algorithm SHA256-RSA based on asymmetric keys instead of MD5 or HMAC-SHA256

• No longer requires HTTPS client certificate (only requires the certificate serial number)

• Uses AES-256-GCM to encrypt and protect the key information in the callback

2. SDK Access

Official SDK（containing language versions of Java、PHP and GO）. Merchants are recommended to develop applications based on the official SDK provided by WeChat Pay. SDK encapsulates requested signatures and response verification for merchants' technical personnel, which simplifies the development of merchant systems.

3. Merchant Independent Access

he Rules describes basic conventions of WeChat Pay API V3, including Data Format, Parameter Compatibility, Handling Errors, and UA Description. It also focuses on the new authentication mechanism (certificates / keys / signature) of WeChat Pay API V3. You can follow our Development Guide and use command lines or a programming language you are familiar with to practice Signature Generation, Signature Verification, Decrypting Certificate, and Callback Message, and Encrypting and Decrypting Sensitive Information step by step.