webhook

advancedwidespread

A webhook is an automated notification between two programs: when something happens in one, it immediately notifies the other at a predefined URL.

In plain terms

Imagine you are waiting for a package. You can call the courier company every hour to ask if it has arrived, or you can give them your phone number, and they will notify you when the courier has set off. A webhook is the second solution, but between programs: you do not need to keep asking; the other party signals as soon as there is news.

In practice, this is a web address that you provide to one service, for example, the payment system of your online store. When an event occurs there (payment, new order, uploaded file), the system sends a short, machine-readable message to this address about what happened.

It is useful because different software systems can react to each other almost instantly without human involvement. In the world of AI agents, it matters because a webhook can even start an agent: a complaint letter arrives, and the agent gets to work on its own.

How it works

On the receiving end, a web address (URL) is created behind which a program awaits incoming messages.
You set this address in the sender service and select which events you want to be notified about, such as 'successful payment' or 'new comment'.
When the event occurs, the sending system initiates a web (HTTP) request to the specified address, containing the event data, usually in JSON format.
The receiving program checks whether the message truly came from the expected sender (usually based on a signature created with a shared secret key), then quickly confirms receipt.
It then performs its own task: issuing an invoice, sending a message, or launching an agent. If confirmation is missing, the sender typically retries multiple times.

An everyday example

You order a book online and pay by credit card. As soon as the payment succeeds, the payment provider notifies the online store via a webhook; upon receiving this signal, the store sends the confirmation email and starts packing. This is why you receive the email within seconds.

Who is affected

developerThey set up and secure webhooks when they need to connect two systems, or an agent and an external service. → Code

entrepreneur, executiveMuch of the automation between online stores, invoicing systems, customer relationship management tools, and agents relies on webhooks, so this determines how much manual work can be saved.

marketerForm submissions, sign-ups, and purchases reach newsletter and campaign management tools instantly via webhook. → Marketing

employeeIn no-code automation tools, you often connect two applications using a webhook, for example, by having a notification arrive immediately in the team's chat channel when a form is filled out. → Work & HR

A common misconception

MythA webhook is the same as an API, just under a different name.

In realityIn a traditional API call, you ask and get an answer; with a webhook, the other system tells you automatically when something happens. The two complement each other, and most services offer both.

Limits and risks

The webhook address is a web address accessible from the internet, so without signature verification, anyone who learns or guesses it can send false messages to it.
Messages may be lost, delayed, arrive out of order, or be duplicated, so the receiving program must be written to avoid processing the same event twice.
It is a one-way signal and often contains only the most important event data; for details, data often needs to be queried separately via API.
If a webhook launches an agent, the incoming message text may contain misleading instructions (prompt injection), so the agent should not treat it as a trusted command.

Similar, but not the same

API – You call the API when you need data, while the webhook notifies you automatically when an event occurs.
polling – In polling, your program checks for updates at regular intervals, whereas with webhooks there is no unnecessary querying; a message arrives only when the actual event occurs.
push notification – A push notification is intended for a person on their phone or browser, whereas a webhook is a message sent to a program for machine processing.

Related concepts

Broader

API, integration, automation, event-driven architecture

Narrower

incoming webhook, outgoing webhook, webhook signature

On the edge

endpoint, JSON, HTTP request, workflow automation, AI-agent

A brief history

The term was coined by American developer Jeff Lindsay in 2007 as a web version of the word "hook" (a hook, a point of attachment) long used in programming. It spread widely in the 2010s through code repositories and payment services.

Where things stand

At the end of 2026, the webhook is the basic tool for connecting web services, offered by almost every payment, code-hosting, chat and automation platform. In agent systems it has taken on a new role: a webhook often starts the agent, or the agent uses one to report that a long-running task is finished.

Status: 2026 November

Also known as

webhook · web hook · webhookok · web recall · HTTP callback · web callback · reverse API · reverse API

Sources

This entry was machine-edited and has undergone machine expert review; the “In the news” section updates automatically from Agent Age stories.