In plain language
It is the useful content being delivered, such as contact fields or order items, separate from routing and protocol metadata.
Example
A webhook payload contains an event ID, customer ID, amount, and payment status.
Related terms
JSON · API · Webhook · Data Mapping
Common misconception
A payload is not always JSON and should not be trusted merely because it came from a familiar endpoint.
Implementation guidance
Document its schema and version, validate types and required fields, limit size, redact secrets from logs, and reject unexpected content safely.