What are Webhooks? Is It Different From API? Explained with Examples

Webhooks are like triggers, they let two online applications talk to each other when something happens in either of them. For example, using webhooks Twilio routes phone calls to your phone number. In this case, the event is- receiving the phone call on Twilio, and the trigger is- routing the call to your phone number. You see, a webhook is to make communication possible between two applications by pushing data back and forth.

What is Webhook?

From the introduction, we have understood that webhooks are used to share real-time information between two platforms whenever a certain event occurs.

Other familiar names for webhook are web pullback and HTTP Push API. Unlike API, it is driven by events rather than requests. Also, API (Application Programming Interface) provides two-way communication between applications based on requests, on the other hand, webhooks provide only one-way communication that too based on events. It will be not wrong to say that webhooks are like lightweight APIs. We are going to delve into the elaborated comparison of API and Webhook in the next section of this article.

Webhooks vs API

What is API (Application Programming Interface)?

You can think of API as a doorway through which applications can share information between them. Actually, the word “interface” in the API full form illustrates the key goal of an API.

The function of an API is a lot like a web browser. For example, a browser act as an interface for end-users i.e. human. We use a browser for sending, receiving, and updating information over a web server. Just like this, an API lets you do the same thing between two applications.

There are over 23,000 different types of APIs in use and we are only talking about publicly available ones. Apart from that, there are hundreds of thousands of internal APIs are being actively used around the world. Nowadays, it has become one of the most common ways of sharing information between two applications.

Definition of Webhooks

It won’t be wrong to say that webhooks are one of many types of API. A webhook is powered by events, whereas an API is driven by requests. As you know, in API one application makes a request to the second application and gets the relevant response (information). Things are different in webhooks, here the second application sends the data over to the first application when a certain event happens. You might even call it a reverse API. Webhook has become a lightweight solution since more businesses are leaning toward interconnected web applications.

Let’s understand with an example, you want to email via Mailchimp when a customer makes a purchase on your website built on WooCommerce. Rather than Mailchimp constantly asking WooCommerce if a new order is placed or not, it makes more sense for WooCommerce to send over data to Mailchimp as soon as a new order comes in. I hope you understand the purpose of webhooks i.e. instead of requesting the data, the application at the receiving end will wait and the sender application will automatically transfer the data as soon as the event occurs.

Comparison: API and Webhooks

	API	Webhook
1	API is request-based data sharing	Webhook is event-based data sharing
2	With API, you have access to large data sets.	With webhooks, you will only get the data of defined events.
3	You have to manually make the request every time if you want information.	The information will automatically deliver to you as soon as the event occurs.
4	Using an API, you can handle CRUD (Create, Read, Update, and Delete) operations.	Using webhooks, you can only POST information.
5	It is mostly used when data in the server-side application or sender is frequently changing.	Webhooks are ideal in the case where you need real-time data.
6	Creating an API is a complex and difficult process.	Creating a webhook is relatively easier compared to API
7	Real-life Example- It’s like asking the retailer again and again whether the product you want is stocked up or not.	Real-life Example- The retailer will notify you as soon as the product will be in stock.
8	Use Case- Uber uses Google Maps API for checking the map in their application.	Use Case Sending subscribe/unsubscribe status of email list to a CRM system.

Webhook Examples

Now you are familiar with the concept of Webhook, it’s time to get some hands-on experience. And fortunately, there are quite a few platforms that allow you to try webhooks. Here are some examples.

1. GitHub Webhook: Using the webhooks in GitHub, you can automate all manual tasks imaginably. For example, you can use them to update external issue trackers, update a backup mirror, or deploy to a production server.
2. Discord Webhook: Discord provides the in-built functionality of webhooks using which you can get automated messages as well as data updates text messages on your server. For example, you can link Discord and GitHub via webhook and GitHub will send you information about Git pushes to the repository, forks, etc.
3. Slack Webhook: Slack prefers to call them Incoming Webhooks and they post messages from other apps to Slack. We can see these incoming messages as a reply in a thread using a webhook. 

How to Test a Webhook?

Testing webhooks is crucial to ensure that the communication between the applications is reliable and secure. Let’s have a look at how it can be done.

It involves verifying that the webhook is working correctly and is receiving and processing data as expected. The following steps can be followed to test a webhook:

1. Create a test webhook endpoint: Before testing a webhook, it’s essential to create a test endpoint. This endpoint will act as the receiver of the webhook. It can be a simple endpoint created using a programming language like Python or Node.js. The endpoint should accept the incoming data and log it or store it in a database for further analysis.
2. Create a test webhook: To test a webhook, you need to create a webhook that sends data to the test endpoint. You can create a test webhook using various online services like Postman or webhook.site. These services allow you to create a webhook and send test data to it.
3. Send test data: After creating the test webhook, you can send test data to it. This data should simulate the data that the webhook will receive from the production environment. You can use tools like ngrok to create a public URL for your test endpoint, making it accessible to the webhook.
4. Verify the data received: Once the test data is sent, you should verify that the test endpoint received the data and processed it as expected. The test endpoint should log or store the data, making it easy to verify that the data was received correctly. You can also use tools like requestbin.com to inspect the incoming webhook data.
5. Test the error scenarios: Testing error scenarios is essential to ensure that the webhook is reliable and secure. You can simulate error scenarios like timeouts, incorrect data, and server errors to verify that the webhook can handle these scenarios gracefully.

Testing webhooks is a critical step in ensuring that different applications can communicate with each other reliably and securely. By following the above steps, you can test a webhook and ensure that it’s working correctly. Testing error scenarios is equally important to ensure that the webhook can handle different scenarios gracefully. With proper testing, you can ensure that your webhooks are reliable and can provide real-time data to other applications.

Concluding Note

In this blog, we have covered almost everything about webhooks like what are they and how they work. We have also included the in-depth comparison between API and webhooks, so there is no confusion whatsoever. Now you can use these user-defined HTTP callbacks using any server-side programming language. You just need a web application that accepts HTTP requests.