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.
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.
- 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
Register a Webhook URL
You provide a publicly accessible URL to receive webhook events
Event Occurs
A specific event happens in the application (payment, new order, etc.)
POST Request Sent
The system sends an HTTP POST request with event data to your webhook URL
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.
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 |
To start receiving webhooks, provide us with your public webhook URL:
POST https://yourdomain.com/webhooks/order_completedYour 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:
{
"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:
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.")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
Key Takeaways
- Webhooks provide real-time notifications by pushing data when events occur
- 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
What’s Next?
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.
Webhook Resources
Expand your knowledge of webhook implementation and best practices.
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