Webhook vs. API: What's the Difference

When building a website or app, you'll often hear about two important technologies: webhooks and APIs. They both help apps and websites to share data seamlessly and are essential to many features. Though they serve similar functions, they operate on different principles. Understanding these differences is crucial for using them effectively. This article will explain just that.

What is an API?

API stands for Application Programming Interface. It is a set of procedures that facilitates communication between independent websites or applications, allowing one application to access another's features.

For example, the National Weather Service or your country's equivalent agency provides daily weather information. The weather app on your smartphone can communicate with this service via its APIs to fetch the data when needed. This way, you get regular weather updates from the weather agency's software system.

How does an API work?

An API is usually implemented as a library an app developer adds to their codebase. The library provides a set of procedures that can be invoked to complete various tasks. The API library documentation specifies the function calls, the accepted inputs, and the outputs the app gives.

API architecture has two parties: client and server. The software sending the request is the client, and the one giving a response is the server. In our weather app example, the agency's weather database is the server, and the user's weather app is the client. Below is an illustration of an API request and response.

• The weather app (client) sends an API request to the National Weather Service's server. The request uses a specific network protocol (in this case, HTTP) and includes information about the data the client wants to retrieve.
• The server receives the client's request and processes it. The request is validated, authenticated, and authorized. Then the server sends back the requested weather data. If the request has any errors, the server will output an error message.
• The client receives and processes the response, displaying the weather data to the end user.

What is a webhook?

A webhook is an automated response an app gives for a specific trigger event. Experienced programmers are familiar with the concept of a callback, and webhooks are a type of callback used in web applications. Unlike APIs, webhooks are intended to facilitate one-way communication.

To receive data using a webhook, you need to create a script capable of processing the incoming data and make it callable via HTTP or HTTPS. Then you register your script’s URL with the data provider.

An example of a webhook is a tweet automatically created when you write a new blog post. Whenever the blog gets updated, the link to a new post will be instantly shared on your social network. In this scenario, the trigger event is the blog post being published, and the webhook provides specific data related to that event.

How do webhooks work?

A webhook relies on a programmed trigger event. The event can be anything, such as a blog post in our example, a user clicking a button, a certain time of day, or completing a web form. When that event occurs, the webhook activates and automatically completes its required task.

Webhooks are suitable for providing new or updating existing data on an external system when an event occurs. For instance, a weather service might utilize a webhook to automatically alert local authorities when it forecasts a storm in their area. The event is a specific weather measurement, triggering an automatic notification to multiple listening apps. Communication is one-way in this case, unlike the API example where the weather app and the weather agency's database communicate with each other.

Webhook vs. API: Similarities and Differences

Similarities

APIs and webhooks are both designed to exchange data between applications. Webhooks and APIs communicate using similar protocols, allowing applications to get data from an external server. The similarities are so strong that people often debate whether to use a webhook or API for the same functionality.

Differences

The main difference between webhooks and APIs is what triggers the data exchange. With an API, the client requests specific data whenever it’s necessary. A webhook sends data when a condition is triggered, without any external request.

APIs are designed to fetch data and perform actions, while webhooks deliver real-time notifications. The former is two-way communication, and the latter is one-way.

Webhook vs. API: Which Should I Use?

Choosing between API and webhooks is a common question. Developers are often confused about when to use one over the other to implement similar functionality. Several factors play a key role in choosing the proper method, including:

1. Latency requirements

Webhooks are ideal for low-latency scenarios. Imagine you’re using an online service to process large video files. Such tasks are usually time-consuming, and you’ll probably have to check your task’s status a few times via API before it is completed. If you make a call every 10 minutes, you will know the task is completed with an average delay of 5 minutes. More frequent checks would create additional load on the system, making processing even slower while still leaving a certain delay. However, if the service implements a webhook, you will be instantly notified when the job is done, without the need for multiple checks.

2. Complexity

APIs are usually set up to perform more complex functions than webhooks. An API request may include additional parameters to refine the task. If you need to implement a versatile scenario, APIs are the way to go. Webhooks are preferable for simple data transfers.

3. Security

APIs can support advanced security protocols, making them the right choice if security is paramount in your application. That doesn't imply webhooks are insecure, nor are all APIs secure. However, technically, APIs allow more advanced security features, and that's why banking apps, authentication apps, and other security-critical apps prefer APIs.

When Should I Use an API?

APIs are the go-to solution for a wide variety of tasks. They enable seamless communication between two or more apps, exchanging data in machine-readable formats (JSON or XML). Nearly all mobile apps use the client-server architecture, where the client app on the user’s phone sends multiple API requests to the server which takes care of actual data processing.

Real-time, multi-way communication enables APIs to perform many functions that webhooks can't, such as:

1. Pulling traffic data for a navigation app.
2. Using a third-party authentication app to log into a website.
3. Making online purchases and giving real-time feedback to the buyer.

When Should I Use A Webhook?

Webhook usage scenarios tend to be more specific. They are often used for server-to-server communication. With webhooks, data only flows in one direction.

Webhooks make sense when you want to deliver notifications to an end user, such as:

• A videoconferencing app sends automatic reminders 5 minutes before a meeting starts.
• A stock trading app notifies users when a stock they own moves by over 10% daily.
• A weather app notifies users about a severe weather forecast in their location.
• A logistics provider sends a notification to the e-commerce service once the parcel is delivered to the client.

Conclusion

Webhooks and APIs are two critical tools that enable apps to exchange data. They have their respective differences, and it's vital to know when to choose one over the other. We've explained the difference between webhooks and APIs and provided a few examples of when to use either tool. Follow our tips, and you'll likely know the best choice in your unique situation.

FAQs

What Differentiates a Webhook and API?

Unlike APIs, a webhook involves one-way communication. An API is a request-driven interaction wherein an app requests data from an external server and gets a response. In contrast, a webhook is a callback automatically triggered by a specific event.

A webhook sends data automatically once a predefined condition is met. The recipient does not have to initiate the request.

Are Webhooks just REST APIs?

No, a webhook isn't a REST API, although it serves a similar purpose. A webhook sends data without a request, while a REST API needs an initial request to exchange data.

API vs. Webhook: Which is Better?

Neither is inherently better than the other. Each one is preferable for different situations. An API is the best choice for an app retrieving data on demand. A webhook is preferable for an app that needs to receive notifications whenever an event occurs.