What is a webhook in a ledger?

A webhook is an HTTP callback the ledger sends when a transaction or other record changes. You do not poll for every status. You listen. A transaction hook is the same idea scoped to one event type. Deliveries retry. Your handler must be idempotent.

How does a webhook work?

You register a URL. When a transaction moves from queued to applied, or an inflight commits, the ledger POSTs a payload. Your app updates its own state. If you miss the call, the ledger retries. If you process the same delivery twice, the reference or event id must save you.

Webhook vs transaction hook

Transaction hook is a narrower name for a webhook about transactions. Global webhooks can cover more than one resource. The contract is the same: an HTTP POST you must treat as at-least-once. Do not ship a second URL scheme for the same events.

What should the handler do?

Verify the call, look up the transaction by id or reference, and advance your own workflow. Do not post a new ledger transaction from a webhook unless that is a deliberate second movement with a new reference. Loops start that way.

Blnk sends webhooks as records change. Use them for lifecycle status, not as a substitute for reading the transaction. Make the handler idempotent with the same care you use on references. See webhooks.