A webhook is an HTTP-based event notification sent from one system to another when something happens. It lets systems react to events without repeatedly checking for updates.

Visualization of a webhook event trigger sending real-time notifications from a source application to multiple connected systems, services, and databases whenever an event occurs.

Webhooks

Q: How do webhooks work?

A sending system detects an event, creates a payload, sends it to a webhook endpoint, and waits for a response. The receiving system validates the request, processes the event, and returns a success or failure response.

Q: What is a webhook endpoint?

A webhook endpoint is the URL that receives webhook requests. It should be secured, validated, monitored, and owned like any other integration entry point.

Q: What is the difference between a webhook and an API?

An API lets one system request, send, update, or retrieve data. A webhook notifies another system when an event happens. In many integrations, a webhook starts the process and an API call retrieves or updates additional data.

Q: What is the difference between webhooks and middleware?

Webhooks send event notifications. Middleware can receive those notifications, validate them, transform the data, route them, and coordinate downstream actions across multiple systems.

Q: Are webhooks reliable?

Webhooks can be reliable when they include signature verification, payload validation, retry handling, idempotency, logging, monitoring, and clear ownership. They are risky when treated as simple notification URLs.

Q: Why is webhook signature verification important?

Signature verification helps confirm that the webhook came from the expected sender and that the payload was not modified. Important workflows should not trust unverified webhook requests.

Q: Why do webhooks need deduplication?

Webhook events may be retried or delivered more than once. Deduplication prevents the same event from creating duplicate payments, records, emails, tasks, or workflow actions.

Q: When should webhooks be used?

Webhooks should be used when another system needs to react after a specific event, such as a payment confirmation, booking update, form submission, order change, lifecycle update, or system alert.

Event Notifications Between Systems

IntegrationAutomationTechnicalSystem

Author: Steven Hsu
Published: 30/05/2026
Updated: 30/05/2026

Webhooks are event-based notifications that allow one system to tell another system when something has happened.

Instead of repeatedly asking an API whether something changed, a webhook sends a message when a specific event occurs. This makes webhooks useful for payment confirmations, form submissions, booking updates, account changes, order events, CRM lifecycle changes, and system alerts.

Webhooks help systems react to events without waiting for manual checks or repeated polling.

A good webhook setup is not just a URL that receives data. It needs secure delivery, payload validation, retry handling, deduplication, logging, monitoring, and clear ownership.

What Is a Webhook?

A webhook is an HTTP-based message sent from one system to another when a specific event happens.

One system acts as the sender. Another system provides a webhook endpoint that listens for incoming event payloads. When the event occurs, the sender sends data to that endpoint.

For example, a payment platform may send a webhook when a payment succeeds. A CRM may send a webhook when a lifecycle stage changes. A booking system may send a webhook when a reservation is confirmed. A form tool may send a webhook when a form is submitted.

The webhook does not ask for data repeatedly.

It reacts when something happens.

Core Idea

A webhook is an event notification. It tells another system that something happened and sends enough context for the receiving system to respond.

Why Webhooks Matter

Webhooks matter because many business workflows depend on timely event updates.

A payment confirmation may need to update an order. A booking confirmation may need to notify operations. A form submission may need to create a CRM record. A lifecycle change may need to start a nurture workflow. A failed payment may need to trigger a recovery process.

Without webhooks, systems may need to poll APIs repeatedly to check whether anything changed. Polling can be inefficient, delayed, and harder to scale.

Webhooks allow systems to respond closer to the moment an event occurs.

This makes them useful for event-driven workflows where timing matters.

How Webhooks Work

A webhook usually follows a simple flow.

Step	What Happens
Event Occurs	Something happens in the sending system.
Payload Created	The sending system prepares event data.
Request Sent	The sender sends an HTTP request to the webhook endpoint.
Endpoint Receives	The receiving system accepts the request.
Validation Happens	The receiver checks signature, source, payload, and event type.
Action Runs	The receiving system updates records, triggers workflows, or logs the event.
Response Returned	The receiver returns a success or failure response.

The webhook sender usually expects a response.

If the receiver confirms success, the delivery may be marked as complete. If the receiver fails, times out, or returns an error, the sender may retry depending on the platform’s delivery rules.

Webhooks vs APIs vs Middleware

Webhooks, APIs, and middleware often work together, but they are not the same thing.

Concept	Main Role	Example
API Integration	Lets systems request, send, update, or retrieve data.	A CRM requests customer details from another system.
Webhook	Notifies another system when an event happens.	A payment platform sends a payment success event.
Middleware	Routes, transforms, validates, and orchestrates data between systems.	A middleware layer receives a webhook, transforms the payload, and updates CRM and reporting systems.

A webhook may start the workflow.

An API may retrieve more detail after the webhook arrives.

Middleware may process and route the webhook to the right destination.

The important point is that webhooks are event-driven. They are useful when the system needs to react to something that already happened.

Common Webhook Use Cases

Webhooks are useful when one system needs to notify another system quickly and reliably after an event.

A payment platform can send a webhook when payment succeeds, fails, is refunded, or requires action. This helps order, booking, finance, or customer communication workflows react to payment status without waiting for manual checks.

Webhooks are strongest when the event has a clear downstream action.

Webhook Payloads

A webhook payload is the data sent with the event notification.

The payload usually includes the event type, event ID, timestamp, source system, object details, and relevant data fields.

A payment webhook may include payment status, transaction ID, amount, currency, customer reference, and event type. A booking webhook may include booking ID, guest reference, dates, room type, status, and payment state.

A simple payload may look like this:

{ "event": "booking_confirmed", "event_id": "evt_10293", "created_at": "2026-05-30T09:00:00Z", "booking": { "booking_id": "BK-10293", "status": "confirmed", "value": 1250, "currency": "USD" } }

Payloads should be treated carefully.

The receiving system should validate the payload before trusting it. Required fields, event type, source, signature, IDs, and value formats should be checked before any important workflow runs.

Webhook Security

Webhook endpoints are public or semi-public receiving points, so security matters.

A webhook endpoint should not trust every incoming request just because it reaches the correct URL.

Secure webhook handling usually includes:

Signature verification
Secret management
HTTPS
Source validation where available
Timestamp checks where supported
Payload validation
Idempotency handling
Limited data exposure
Logging and monitoring

Signature verification is especially important. It helps confirm that the webhook came from the expected sender and was not modified in transit.

A webhook should not trigger important business actions until the request is verified.

Security Risk

A webhook endpoint should verify the sender and payload before updating records, triggering workflows, or accepting the event as trusted.

Webhook Delivery and Retries

Webhook delivery is not always guaranteed on the first attempt.

The receiving endpoint may be unavailable. The request may time out. The server may return an error. The payload may fail validation. A system may be temporarily down.

Many platforms retry failed webhook deliveries, but retry behavior varies by platform.

That means the receiving system should be designed for repeated delivery.

A webhook event may arrive more than once. The same event may be retried after a temporary failure. The receiving system should avoid processing the same event multiple times if that would create duplicate records, duplicate emails, repeated payments, or duplicated workflow actions.

This is where idempotency matters.

Idempotency and Deduplication

Idempotency means the same event can be processed more than once without creating incorrect duplicate outcomes.

For webhooks, this usually means the receiving system checks a stable event ID, transaction ID, booking ID, order ID, or external reference before taking action.

For example, if a payment_succeeded webhook arrives twice, the system should not create two payments, two invoices, or two confirmation emails. It should recognize that the event has already been handled.

Deduplication logic should be planned before webhook workflows go live.

Problem	Risk	Practical Control
Duplicate webhook delivery	Same workflow runs twice.	Store and check event IDs.
Replayed request	Old event is sent again.	Check timestamp and signature where supported.
Multiple related events	Events arrive in unexpected order.	Use object status and source-of-truth checks.
User refresh or retry	Duplicate downstream action.	Use transaction, order, lead, or booking IDs.

A reliable webhook setup assumes duplicate or delayed delivery can happen.

Webhooks and Error Handling

Webhook failures should be visible.

If the receiving endpoint fails silently, the business may lose important events without noticing. Payment confirmations may not update. Booking changes may not sync. Form submissions may not reach CRM. Operational alerts may disappear.

Webhook error handling should define:

Failure Type	Response
Invalid signature	Reject the request and log the attempt.
Missing required field	Reject or quarantine the event for review.
Temporary system outage	Retry or queue the event where possible.
Duplicate event	Acknowledge but avoid duplicate processing.
Unknown event type	Log and ignore or route for review.
Downstream system failure	Store the event and retry later.

The receiving system should respond quickly, log clearly, and avoid running fragile workflows directly inside the webhook handler when the process is complex.

For critical workflows, webhooks often work best when received, validated, stored, acknowledged, and then processed asynchronously.

Webhooks and Middleware

Middleware can make webhook handling more reliable.

A webhook may arrive from a payment platform, booking engine, form tool, CRM, ecommerce platform, or internal system. Middleware can receive the webhook, validate the payload, transform fields, check source-of-truth rules, deduplicate the event, and route it to the right system.

This is useful when one webhook should trigger several downstream actions.

For example, a booking confirmation webhook may need to update the CRM, notify operations, send analytics data, update reporting, and trigger customer communication. Middleware can coordinate those actions without forcing the booking system to connect directly to every destination.

Webhooks provide the event.

Middleware manages the response.

Webhooks and API Integration

Webhooks often work together with API integrations.

A webhook may tell a system that something happened, but the payload may not include every detail needed. The receiving system may then use an API call to retrieve more information.

For example, a payment webhook may notify the system that payment succeeded. The receiving system may then call the payment API to retrieve full payment details before updating finance records.

A CRM webhook may notify another system that a lifecycle stage changed. The receiving system may then call the CRM API to retrieve the latest contact or account details.

This combination is common.

The webhook starts the process. The API completes the data retrieval or update.

Common Webhook Mistakes

Treating webhook delivery as guaranteed
Trusting requests without signature verification
Processing duplicate events more than once
Running complex workflows directly inside the webhook handler
Failing to store event IDs
Ignoring retry behavior
Not logging failed deliveries
Sending sensitive data unnecessarily in payloads
Assuming events always arrive in order
Letting webhook endpoints become undocumented

The biggest mistake is treating a webhook as a simple notification URL.

A reliable webhook setup needs security, validation, deduplication, retry handling, monitoring, and ownership.

Best Practices for Webhooks

Webhooks work best when they are treated as operational infrastructure, not just developer plumbing.

Define Event

Start with the trigger.

Decide which event should send a webhook and what business process it supports. A payment success, booking confirmation, form submission, or lifecycle change should each have a clear downstream purpose.

Define Event

Start with the trigger.

A good webhook setup should be secure, observable, and resilient enough to handle imperfect delivery.

Webhook Checklist

Before launching a webhook, the following questions should be clear:

Question	Why It Matters
What event triggers the webhook?	Clarifies the business purpose.
What endpoint receives it?	Defines ownership and implementation.
How is the sender verified?	Prevents untrusted requests.
What payload fields are required?	Supports validation and processing.
What event ID prevents duplicates?	Supports idempotency.
What happens if delivery fails?	Supports recovery.
What happens if the downstream system fails?	Prevents data loss.
Where are events logged?	Supports troubleshooting.
Who owns the webhook?	Clarifies maintenance responsibility.
How will the webhook be tested?	Reduces launch risk.

A webhook that cannot be tested, monitored, or explained should not be treated as reliable.

Final Thoughts

Webhooks make integrations more responsive by allowing systems to react when events happen.

They are especially useful for payments, bookings, forms, lifecycle changes, orders, alerts, and other event-driven workflows. But webhooks are only reliable when the receiving system handles them properly.

A strong webhook setup verifies the sender, validates the payload, prevents duplicate processing, monitors delivery, and defines what happens when something fails.

Webhooks are simple in concept. They require discipline in operation.

Frequently Asked Questions

Practical answers about webhooks, event payloads, API integration, middleware, retries, signatures, and webhook reliability.

What is a webhook?

How do webhooks work?

What is a webhook endpoint?

What is a webhook payload?

What is the difference between a webhook and an API?

What is the difference between webhooks and middleware?

Are webhooks reliable?

Why is webhook signature verification important?

Why do webhooks need deduplication?

When should webhooks be used?