What a webhook is
A webhook is an automated HTTP request that one application sends to another the moment a specific event happens. When an order is paid, a user signs up, or a build finishes, the source system fires off a small message, usually JSON, to a URL you control. Your app receives it and reacts right away.
The key idea is direction. With a normal API call, your app asks the other system "is there anything new?" again and again. With a webhook, the other system tells you the instant something changes. That is why people call webhooks a reverse API or an event-driven push.
In plain words
Imagine waiting for a parcel. Polling an API is like phoning the depot every ten minutes to ask if it arrived. A webhook is the courier ringing your doorbell the moment it lands. You do not waste calls, and you hear about it the second it happens.
When to use webhooks
- Real-time reactions. Send a Slack alert when a payment fails, or start a workflow when a form is submitted.
- Connecting tools. Stripe, GitHub, and most automation platforms use webhooks to glue services together without custom polling.
- Saving resources. No more hammering an API on a timer. The event arrives only when there is something to report.
To set one up, you give the source system a URL (the endpoint) and pick which events to subscribe to. From then on, that system posts data to your endpoint whenever those events occur.
Common pitfalls
- Anyone can post to a public URL. Verify each webhook is genuine, usually with a signature the sender includes. Without that check, an attacker can fake events.
- Delivery is not guaranteed. Networks fail and your server may be down. Expect retries, handle the same event arriving twice (make your handler idempotent), and confirm receipt fast with a 200 response.
- Slow handlers cause timeouts. Senders give you only seconds. Acknowledge immediately, then do the heavy work in the background.
Related articles:
- What is an API? - The broader way apps talk to each other, which webhooks turn around.
- What is an API key? - How systems prove who they are when they call each other.
- Automating business processes with AI agents - Where event-driven triggers like webhooks fit into automation.
Want to stay one step ahead?
Don't miss our best insights. No spam, just practical analyses, invitations to exclusive events, and podcast summaries delivered straight to your inbox.