Understanding Webhooks

Webhooks are a simple yet powerful tool for apps and web services to notify one another when events occur, enabling your applications to respond and take further action as needed. This guide will provide an overview of webhooks and how they work, with examples of common use cases and best practices for implementation.
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What is a webhook?

Webhooks are user-defined HTTP callbacks triggered by specific events in a source application. Put more simply, they are automated messages sent between servers and apps when “something happens.”

You probably experience webhooks every day without realizing it, whether it’s Instagram adding you to the “browsed steak knives” list after you dwelled on a set of knives, or your bank texting you when your account balance drops below a certain threshold.

Webhooks play an important role in modern web applications and can be used for a variety of purposes that can help you improve your customer experience and streamline your business processes. This guide is a short introduction to webhooks with examples and resources for further exploration.

Core components of a webhook

Event
This is the trigger or the action that starts the process. An event can be any specific action or occurrence in the source application which initiates the webhook process, such as a database update, a server event, or a user action.
Payload
Once the event occurs, a payload, typically in JSON format, is created. This payload contains information about the event.
Webhook URL
This is the endpoint (URL) where the payload is sent. Each webhook URL is unique and typically linked to a specific action or response in the receiving application, e.g., https://api.example.com/webhooks/order-update. This endpoint is typically a RESTful API within the receiving application, designed to handle incoming webhook data.

Following is an example of an ecommerce event payload, which is sent as an HTTP POST request to the webhook URL, with the event type and timestamp included in the payload:

POST /webhooks/order-update HTTP/1.1
Host: api.example.com
Content-Type: application/json

{
  "event": "order_created",
  "timestamp": "2023-11-14T12:30:45Z",
  "order": {
    "id": 123456,
    "status": "pending",
    "items": [
      {
        "product_id": 98765,
        "name": "Wireless Headphones",
        "quantity": 1,
        "price": 99.99
      },
      {
        "product_id": 12345,
        "name": "Bluetooth Speaker",
        "quantity": 2,
        "price": 49.99
      }
    ],
    "total_price": 199.97,
    "customer": {
      "customer_id": 7890,
      "name": "John Doe",
      "email": "johndoe@example.com",
      "shipping_address": {
        "street": "123 Main St",
        "city": "Anytown",
        "state": "CA",
        "zip": "12345",
        "country": "USA"
      }
    }
  }
}
Webhook Receiver
The server that receives the webhook payload. It must be configured to accept POST requests and extract necessary information from the payload. The logic within the receiving application that processes the incoming webhook data. This often involves parsing the JSON payload, validating its authenticity, and executing business logic based on its contents.
Security
To ensure data integrity and security, webhooks often include signatures allowing the receiver to verify that the information is indeed from a trusted source such as cryptographic methods and HTTPS. This is especially important when the webhook payload contains sensitive information.
Acknowledgment & Error Handling
The receiver may send back HTTP response codes to acknowledge successful processing or indicate errors, which the source application can use for logging or retry logic.

Webhooks workflow diagram

Now that you have a basic understanding of the components of a webhook, let’s look at how they work together. The following diagram illustrates the typical workflow of a webhook:

  1. Event Detection. The source application detects an event.
  2. Trigger and Payload. The event triggers the webhook, which then sends a payload via an HTTP POST request to the webhook URL.
  3. Webhook URL (Receiver). The webhook URL receives the payload.
  4. Server Action The server at the receiver’s end processes this payload and can optionally send a response to the origination application or server.
sequenceDiagram
    participant U as User
    participant A as Source application
    participant W as Webhook URL (Receiver)
    participant S as Server action

    U->>A: Performs an action
    A->>A: Detects event
    Note right of A: Event triggers webhook
    A->>W: Sends payload via POST
    Note over W: Receives payload
    W->>S: Processes payload
    S->>W: Optional response
    Note over A,W: Communication via HTTPS

Advantages of Webhooks

  • Real-Time Data Transfer: Webhooks provide real-time information transfer, which is faster than polling for updates.
  • Efficiency: They reduce the need for continuous polling, saving resources and bandwidth.
  • Customization and Flexibility: They can be configured for a wide variety of events and responses, making them highly adaptable to specific needs.

Common Implementations

Webhooks are a ubiquitous part of modern web applications and can be used for a variety of purposes. Some common use cases include:

  • E-Commerce Notifications: Triggering inventory updates or order processing in response to a purchase transaction event.
  • CI/CD Pipelines: Triggering build or deployment processes in response to source code repository events.
  • Customer Support: Creating a support ticket when a user submits a form.
  • Social Media: Sending notifications when a user posts a comment or shares a post.
  • User profiling: Sending notifications when a user browses a product or service.
  • Abandoned cart recovery: Sending reminders when a user abandons a cart.
  • Service outages: Sending alerts when a service goes down or is unavailable.

Conclusion

Webhooks offer a powerful, efficient, and real-time way to integrate different systems and automate workflows. Organizations can leverage webhooks to streamline operations, enhance customer experience, and improve system interconnectivity.

Learn more

  • Try out webhook.site to see how webhooks work in practice, test your own callbacks, and inspect webhook payloads. This is a great resource for experimenting with webhooks without having to set up your own server.
  • If you’re not comfortable writing code, check out Zapier or IFTTT. These services allow you to create simple workflows using webhooks and other integrations, and can illustrate the power of webhooks in a few simple clicks.
  • GitHub’s webhook documentation is a great place to start. It’s well-written, and provides a good overview of how webhooks work in practice.