A webhook is an automatic message one system sends another the moment something happens. Instead of your system constantly asking for new data, the other system tells you: a payment succeeds and your system gets notified, a form comes in and the CRM receives the lead. It’s the opposite of cron and scheduling, which checks on a fixed schedule, like walking to the front door every fifteen minutes.
Picture a doorbell at an office. You don’t stand at the door all day asking whether someone has arrived. The bell rings when they do, and that ring is the cue to do the next thing.
Why you care
Webhooks make systems responsive and less wasteful, and they’re where automation chains often start: event happens, webhook fires, the next system acts. For agentic work, a client uploading a file can wake a process at the right moment instead of an agent polling for it. The doorbell has a second lesson: if the bell rings and nobody is assigned to answer it, nothing useful happens. A webhook needs a receiver, a rule for what to do next, and enough error handling that missed signals don’t become silent failures.