Short definition

Webhook — an HTTP request that a system automatically sends to a preconfigured URL when a specific event occurs.

Also known as: HTTP callback, event webhook.

View all terms

A webhook sends an HTTP request from one system to another. Instead of repeatedly checking for changes, the source sends the request as soon as an event happens.

How does a webhook work?

You register a URL with the sending system. When an event occurs, such as a successful payment, a form submission, or a published article, the system sends an HTTP request with the details to that URL. The receiving system verifies the request, processes it, and responds with a status code.

Take an online store that uses a payment provider. When a customer pays, the provider sends a POST request to the store’s webhook URL. The body names the event, such as payment.succeeded, along with the order number, the amount, and a timestamp, and a header carries a signature. The store checks that signature and marks the order as paid. It passes the data on to its accounting software and replies with a 2xx status, so the provider knows the delivery arrived.

What does this mean for a small business?

Webhooks can send new orders to accounting software, leads to a CRM, or form submissions to an inbox without repeated polling or manual updates. The receiving system must be robust because requests may be duplicated, arrive out of order, or be forged.

What should you watch for in a webhook?

  • verify signatures before processing anything;
  • make processing idempotent so retries do not repeat the effect;
  • respond quickly and process long-running work asynchronously;
  • log failed deliveries and provide a retry or reconciliation mechanism;

How it relates to other website choices

Webhook vs. API: the difference is who starts the conversation. With an API, your system asks for data, so to notice a change it has to poll the API again and again. With a webhook, the source pushes one request the moment the event happens. Technically, a webhook is itself an HTTP call to an endpoint you expose, which is why it is sometimes called a reverse API. In practice the two work together: the webhook signals that something changed, and an API call fetches the full, current details.

Together, they support workflow automation and controlled integrations with AI agents.