[Glossary](https://blnkfinance.com/glossary) Webhook # What is a webhook in a ledger? Webhook 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](https://docs.blnkfinance.com/webhooks/overview). Related terms - [Transaction lifecycle](https://blnkfinance.com/glossary/transaction-lifecycle) - [Transaction](https://blnkfinance.com/glossary/transaction) - [Identity](https://blnkfinance.com/glossary/identity) - [Reconciliation](https://blnkfinance.com/glossary/reconciliation)