Webhooks: When systems react
Learn how one system notifies another immediately after an event.
- 7 minutes
- foundation
- Reviewed 2026-07-16
What is it?
A webhook is an HTTP message sent to a URL when an event occurs. Its payload describes what happened so the receiving workflow can react.
Why does it matter?
Polling wastes calls and introduces delay. Webhooks let an order, form, or repository start work close to real time.
The mental model
An API is usually called when you ask. A webhook calls you when something happens.
A simple example
A form service posts a new-submission event to a workflow URL. The workflow validates the payload and creates a record.
What it is not
A webhook is not a guarantee that downstream work succeeded. Receivers still need authentication, validation, retries, duplicate protection, and monitoring.
Learn this first
These ideas make the lesson easier to place.
- APIs
- Events
Your first 60 minutes
Use one focused hour to make the idea concrete.
- Compare a five-minute polling schedule with an event trigger.
- Inspect a sample webhook payload.
- Send a test payload to a local or platform test endpoint.
Build this first
Receive a sample form event, verify a shared secret, store its event ID, and return a clear success response.
When not to use it
Use polling when the source offers no webhook, delivery is unreliable without recovery, or a slow daily refresh is entirely sufficient.
What to learn next
Learn structured data and reliable workflow failure handling.