Webhooks API Documentation Guide

Learn how webhooks deliver real-time notifications instead of requiring constant API polling. This guide explains webhook implementation, security, best practices, and documentation standards for modern APIs.

Table of Contents

Alright, so you’ve spent a good chunk of time building, testing, and documenting REST APIs. Feels great, right? But here’s the thing: polling sucks.

Imagine constantly refreshing your email inbox to see if you’ve got mail. Annoying, isn’t it? Well, that’s exactly what happens when clients keep sending GET requests to check if new data is available. Enter webhooks—the solution to avoid being that impatient person hitting “refresh” every five seconds.

Webhooks don’t wait for you to ask. They tell you when something important happens. That’s right—real-time notifications, no unnecessary API calls, and fewer server meltdowns.

REST vs Webhooks
REST APIs are pull-based (client requests data), while webhooks are push-based (server sends data automatically). Understanding this fundamental difference is key to implementing the right solution for your use case.

What is a Webhook?

A webhook is an event-driven API callback that sends data to a specified URL when something happens in an application. Instead of constantly asking, “Hey, got any updates?”, webhooks just notify your system the moment something changes.

Real-World Webhook Examples
  • A payment gateway (like Stripe) sends a webhook when a payment succeeds.
  • A GitHub repo fires a webhook when a new commit is pushed.
  • A project management tool notifies your app when a task is completed.

Essentially, webhooks are the instant coffee of APIs—quick, effective, and always ready when you need them.

How Webhooks Work

1

Register a Webhook URL

You provide a publicly accessible URL to receive webhook events

2

Event Occurs

A specific event happens in the application (payment, new order, etc.)

3

POST Request Sent

The system sends an HTTP POST request with event data to your webhook URL

4

Process Webhook Data

Your server receives and processes the webhook payload

Webhooks vs REST APIs: What’s the Difference?

Feature REST API Webhook
Communication Model Client requests information Server sends information automatically
Data Flow Pull (Client asks) Push (Server notifies)
Use Case Structured queries & data retrieval Real-time event notifications
Efficiency Can be slow due to repeated polling Faster since updates come instantly
Server Load Higher (frequent requests) Lower (only when needed)
Example GET /orders → Returns all orders Order completed → Sends event to your URL

REST APIs are like checking in at the airport every 5 minutes to see if your flight is boarding. Webhooks are like getting a text when it’s time to go.

When to Use Each
Use REST APIs when you need to query data on demand or perform operations. Use webhooks when you need to know immediately when something happens or to avoid constant polling.

How to Document Webhooks in API References

Since webhooks push data instead of waiting for requests, documenting them requires a slightly different approach than REST APIs. Here are the essential components of comprehensive webhook documentation:

1. Webhook Overview Section

Every webhook documentation should start with a clear overview that explains:

Webhooks allow you to receive real-time notifications when an event occurs in our system. 
Instead of polling our API, you can subscribe to specific events and receive an HTTP POST request 
to your webhook URL when they occur.

2. Webhook URL Setup Documentation

Field Type Description
URL string Your endpoint that listens for webhook events
Method POST Webhooks always send data via POST requests
Content-Type application/json Webhook payloads are sent in JSON format
Secret Key string Used to verify that the webhook request is authentic
Example Configuration

To start receiving webhooks, provide us with your public webhook URL:

POST https://yourdomain.com/webhooks/order_completed

Your server must be configured to accept POST requests, extract the data, and process it accordingly.

3. Webhook Event Types

Document all the events that your system can send webhooks for:

Event Name Description When It's Triggered
order.completed Triggered when an order is successfully completed After payment is processed and order is confirmed
invoice.paid Fired when an invoice payment is received When payment for an invoice is successfully processed
user.signup Sent when a new user registers on the platform After user confirms email address

Users can subscribe to specific events based on their needs.

4. Webhook Payload Format

The most important part of webhook documentation is describing what data is sent. Always include detailed examples for each event type:

Example: order.completed Event
Request Body
Request Headers
{
  "event": "order.completed",
  "data": {
    "order_id": "12345",
    "customer": {
      "name": "John Doe",
      "email": "john@example.com"
    },
    "total": 49.99,
    "currency": "USD"
  }
}

For each payload property, provide a detailed explanation in a table format:

Property Type Description
event string The name of the event that triggered this webhook
data object Contains all the relevant information about the event
data.order_id string Unique identifier for the order
data.customer object Information about the customer who placed the order
data.total number The total amount of the order
data.currency string Three-letter ISO currency code

Securing Webhooks

Since webhooks are publicly accessible, security is crucial. Anyone could send a fake request to your webhook endpoint, so you must verify webhook authenticity before processing the request.

Signature Verification

Every webhook request should include a signature header. Here’s how to verify it:

Python Code for Signature Verification
import hmac
import hashlib

secret = "your-webhook-secret"
payload = '{"event":"order.completed","data":{"order_id":"12345"}}'
received_signature = "a94a8fe5ccb19ba61c4c0873d391e987982fbbd3"

calculated_signature = hmac.new(
    key=secret.encode(),
    msg=payload.encode(),
    digestmod=hashlib.sha256
).hexdigest()

if calculated_signature == received_signature:
    print("Webhook verified!")
else:
    print("Invalid webhook request.")
Security Best Practice
Always verify the signature of incoming webhook requests before processing them. Processing unverified webhooks could lead to security vulnerabilities.

Handling Webhook Responses

Response Code Meaning When to Use
200 OK Webhook received successfully When you've successfully received the webhook
400 Bad Request Invalid request format When the webhook payload is malformed
401 Unauthorized Signature verification failed When the signature doesn't match
500 Internal Server Error Something went wrong on your server When your webhook handler encounters an error

Most webhook providers will retry failed webhook deliveries 3-5 times with an exponential backoff.

Webhook Best Practices

🔒

Use HTTPS

Always use HTTPS for webhook endpoints to encrypt data in transit

✅

Validate Signatures

Verify webhook authenticity using the provided signature

📝

Log Webhook Requests

Store webhook payloads for debugging and audit purposes

⚡

Respond Quickly

Return a 200 response immediately and process data asynchronously

🔄

Handle Retries

Be prepared to receive the same webhook multiple times

🧪

Test with Simulated Events

Use sandbox environments to test webhook handling before going live

Frequently Asked Questions About Webhooks

Get answers to the most commonly asked questions about webhooks, including implementation details, security concerns, and troubleshooting tips.

Webhook Basics

Implementation

Troubleshooting

Key Takeaways

  • Webhooks are event-driven callbacks that push data to your application when events occur, eliminating the need for polling
  • They eliminate the need for constant polling, reducing server load and latency
  • Always verify webhook signatures to ensure requests are authentic
  • Respond to webhooks quickly (with 200 OK) and process the data asynchronously
  • Proper documentation should include event types, payload formats, and security details
  • Webhooks are ideal for event-driven architectures where immediate updates are needed

Now that you understand how webhooks work and how to document them, you’re ready to implement event-driven architectures in your APIs. In the next chapter, Writing API Documentation, we’ll explore broader techniques for creating effective API documentation.

Test Your Knowledge

Check your understanding of webhooks with this quiz.
Question 1 of
Technical Writing Expert

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Essential Webhook Resources

Deepen your understanding of webhooks with these carefully selected resources.

External Resources

Tools & APIs

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