What Is a Webhook? Explained Simply

What a webhook is

A webhook is a way for one application to automatically send a message or data to another application the moment a specific event happens. Technically, it is an HTTP request (usually carrying data as JSON) that a source service sends to a URL you provide, essentially a 'reverse API': instead of your app asking the service for information, the service calls your app when there is something to report. This makes webhooks the backbone of real-time, event-driven communication between web services.

The problem it solves

Imagine you want to know when a payment succeeds, a form is submitted, or a build finishes. Without webhooks, your app would have to repeatedly ask the other service 'has it happened yet?', a technique called polling. Polling is inefficient: ask too often and you waste resources and hit rate limits; ask too rarely and you get stale information. Webhooks flip this around: the service notifies you the instant the event occurs, so you get timely updates without constant checking.

How it works

Setting up a webhook typically means giving a service a URL (an endpoint on your server) and telling it which events you care about. When one of those events happens, the service sends an HTTP POST request to your URL containing details about the event. Your endpoint receives that request, reads the data, and does whatever you need, update a database, send a notification, trigger another process. From your side, it is just a small piece of code waiting to handle incoming requests.

Webhooks vs polling an API

The core distinction is direction and timing. With a normal API, your app initiates the conversation, requesting data when it wants it (pull). With a webhook, the service initiates, pushing data to you when an event fires (push). Polling repeatedly pulls and often gets 'nothing new'; webhooks deliver exactly when there is something new. For real-time reactions, webhooks are far more efficient. APIs and webhooks are complementary, many services offer both, and you choose based on whether you need to fetch on demand or react to events.

Where you encounter them

Webhooks quietly power countless everyday integrations. A payment processor uses one to tell a store when a transaction completes. A code repository fires a webhook to trigger an automated build or deployment when you push changes. Chat apps use them to post messages from external tools. Automation platforms rely heavily on webhooks to connect different services, 'when X happens in app A, do Y in app B'. If two online services react to each other in real time, a webhook is often what connects them.

Practical considerations

Because a webhook endpoint receives data from the outside, a few practices matter. Verify that incoming requests genuinely come from the expected source (many services sign their webhooks so you can confirm authenticity), respond quickly so the sender does not consider the delivery failed, and handle the occasional duplicate or retried delivery gracefully. Understanding webhooks demystifies a huge amount of modern automation, they are the simple but powerful mechanism that lets the web's many services notify each other the moment things happen.

Related on Skillo

See also: What is an API? Explained for beginners, What is JSON? The web's data format explained.

Sources

• Webhook - Wikipedia

Published date reflects the original event date (2025-11-04). This article is original Skillo editorial written from the sources above; facts were verified in September 2026.