Webhooks vs APIs: What's the difference?

Let's explore the similarities, differences and potential use cases for webhooks and APIs, helping you decide when and where to use them in your projects.
March 23, 2023


Whether facilitating real-time interactions on social media or sending automatic notifications about recent transactions, applications must provide their services as quickly as possible. Moreover, many rely on other applications to provide all of their functionality.

There are two primary ways that apps communicate: webhooks and application programming interfaces (APIs). These two technologies share some similarities. However, they are anything but interchangeable, providing different base functionalities for different purposes. Therefore, choosing between them boils down to the type of communication that your app requires.

In this post, we'll take an in-depth look at the similarities, differences, and potential use cases for webhooks and APIs. By the end, you’ll be able to determine when it’s most appropriate to use each tool.

Interprocess communication: the difference between webhooks and APIs

Both webhooks and APIs are used to send lightweight data between applications, but that's where their similarities end. Let’s take a look at some of the differences between the two.

What's a webhook?

A webhook is an event-based service that enables you to send data from one application to another when a specified event occurs. The event triggers an automated action that sends the information from the source application to the recipient — the client or target application — via an HTTP (or HTTPS) request.

Webhooks work in three steps. First, the developer defines the event — typically a specific change. Then, the webhook “listens” for that event.

Next, when the event happens, the source makes an HTTP POST request (often containing JSON) to the callback URL which is defined in the client/target application. The callback URL is an endpoint that contains the logic that executes in response to an event.

Below is a typical webhook request flow chart:

webhook request flow diagram

Webhook use cases

Webhooks function to prevent the target application from having to repeatedly ask for data. Instead, they receive one-way data updates automatically, when a predefined trigger occurs. This design has made webhooks essential in systems like news apps and ecommerce sites, which must send notifications or process data in real time.

One potential use case for a webhook is to serve as a trigger for a website build. For example, consider a static website that must be rebuilt each time its data changes in its CMS. You could define a webhook that listens for the update, then sends an HTTP request to the designated endpoint to trigger a build. With this method, you can ensure that your site always stays up to date. 

Similarly, you could use webhooks to receive Slack notifications about important updates, such as build failures, potential cyber attacks, or anything related to your workflows. 

Webhooks are unidirectional. This means that the client or recipient app cannot send information back to the source application. Check out our ultimate guide to Contentful webhooks for more details on how they function in a composable content platform.

What's an API?

APIs are used by two applications to exchange data. There are several types, all with acronyms, so you’ll often hear about GraphQL or REST APIs. Whereas a webhook only occurs once when an event triggers, API calls can create a “conversation” through a cycle of requests and responses. 

First, the client application sends an HTTP request to the server according to predetermined specifications. Then, depending on the type of request and included parameters, the server responds by sending back meaningful data to the client.

For example, imagine a user checking the weather on their smartphone. The weather app makes an HTTP GET request to a remote server, which then sends back the relevant data. The phone then populates this data in the app for the user to view.

API Request & Response Flow Diagram

API use cases

APIs are the most popular method for connecting and exchanging information between systems. From news apps to a driver using Google Maps for navigation, the universal nature of APIs makes them the cornerstone of modern web interactions.

As such, you can find APIs in just about every industry. They can facilitate communication between internal systems or between a company and its customers.

Developers use APIs when their programs require two-way communication: A client sends something to the server, and the server returns a response. Furthermore, their flexibility enables applications to share complex functions with one another (for example, the Android and iOS version of a weather app will use the same API) so each app can accomplish more without additional feature programming. 

Webhooks and APIs: Choose the right tools

As you’ve seen, APIs remain the predominant choice for web interactions. They allow flexible two-way communication regardless of any differences between the client and source applications.

However, that’s not to say that they can replace webhooks entirely. Both tools are essential to the functionality of modern applications — you just need to choose the right tool for the job.

In fact, webhooks are essentially a more lightweight subset of APIs. Because they only work unidirectionally and handle a limited amount of information, they tend to be less resource-intensive than an API that must constantly poll for new data.

But APIs are the optimal choice when you need to create, modify, or delete data (CRUD); webhooks lack any capability to manipulate information. But if you merely need a notification when certain events occur, webhooks make the most sense.

Wrapping up

Overall, both webhooks and APIs are crucial to the functioning of the web. Both webhooks and APIs are frequently used in the applications we use every day.

The most crucial consideration when deciding between webhooks and API is if the data you wish to view is continuously updated. In this instance, you’ll likely want to use an API instead. 

Regardless of your choice or level of knowledge about APIs and webhooks, Contentful speaks both! Sign up for a free Contentful account and see how our market-leading content platform can support your project or business.

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