Wallet / PassKit Web Service
The PassKit Web Service is a server-side HTTP contract that Wallet pass providers must implement so that Apple Wallet can register devices, enumerate pass serial numbers, fetch the latest pass version, unregister devices, and accept log messages. While Apple does not host this API itself, it specifies the exact endpoints (/v1/devices/.../registrations/..., /v1/passes/{passTypeIdentifier}/{serialNumber}, /v1/log) every provider must expose. APNs is the companion channel for pass-update notifications.