What is the difference between callback and webhook?

Callback and webhook are mechanisms for asynchronous interaction between systems, but they differ in implementation and context of use.

• Callback is a function or method that is passed as an argument to another function and is called after a certain action is completed. Usually, a callback is used within a single application or between components when it is necessary to process the result of an operation.

• Webhook is an HTTP notification that one system sends to another at a pre-defined URL when a specific event occurs. Webhook operates over the network and allows systems to interact in real-time without constant polling.

Example:

• Callback: in JavaScript, you pass a function that will execute after data is loaded.
• Webhook: a payment service sends a POST request to your server when a payment is confirmed.

Thus, a callback is a programming technique within an application, while a webhook is an external notification mechanism via HTTP.