Webhooks vs. APIs: What's the Difference?

Today, APIs and webhooks play a more prominent role in our everyday lives than most people realize. For example, if you've ever used a social media bot, logged into a third-party app using your Google or Facebook account, or clicked the "pay with PayPal" button on an eCommerce website, then you've used an API. And beyond the day-to-day, this technology is also becoming almost ubiquitous in professional spaces. Nearly three in four professionals and a whopping 89% of developers use APIs in their roles[1].

This sharp rise in popularity over recent years is grounded in our need for fast and easy communication. In simple words, to facilitate rapid communication between technology and people, we first need to find a way to make systems talk to each other. And that's where APIs and webhooks come in.

However, many people are still confused about the difference between these two technologies and when it's more appropriate to use one over the other. That's what we're going to clear up today in our guide to webhooks vs. APIs. Let's get into it.

Webhook vs. API: The Difference in a Nutshell

Both webhooks and Application Programming Interfaces (APIs) are intermediary software that allows two apps to talk to each other. However, they both have different ways of working and therefore serve different purposes.

APIs use a request-based method to share data between applications. This means that the requesting app will "ask" the provider app for specific information, and the provider app will return the requested information. APIs are an example of two-way communication between systems.

Webhooks work a little differently. Webhooks use an event-based method to relay data between systems, meaning they only run when a specific event occurs in the source app. They're an example of one-way communication.

To put it simply, APIs do something when you ask them to, while webhooks do something on their own when specific criteria are met. Let's look at a basic example. An email API might continually "call" your email server and ask, "do I have any new emails?". Sometimes, the answer will be yes, and you'll receive the email, and sometimes the answer will be no, and nothing will happen. With a webhook, when the email server receives the email (the event), this will trigger the webhook, and the app will notify you of the email.

Recap: The differences between webhooks and APIs

APIs are request-based, meaning they kick into action when requests come from 3rd party apps.
Webhooks are event-based, meaning they execute when a specific event occurs in the source app.
With APIs, the user sends and requests data. With webhooks, data is sent automatically.
You can think of APIs as “pulling” information, and webhooks as “pushing” information.

Now, let's dive a little deeper into webhooks and APIs and how they work.

What is an API?

Standing for Application Programming Interface, an API is essentially a portal through which information and functionality can be shared between two applications. Lots of existing software relies on APIs to expand functionality, allowing users to get more from their app experiences. APIs can also enable organizations to share information and resources with security, control, and authentication (who can access what and when) being maintained.

For an API to work, a data request is sent in a pre-specified format, which the API then processes before returning the requested information. This requested data is typically delivered in a JSON or XML format. JSON is the more popular language due to its compact style, efficient performance, and similarity to JavaScript (the dominant client-side scripting language on the Web). With that said, some APIs opt for XML because it offers superior document handling capabilities and boosted security. The choice really depends on the purpose of the API.

APIs can also differ in their protocols and architecture. Essentially, the way the API sends and receives data will be different depending on the convention used by the developer. The most common architectural approach is Representational State Transfer, typically shortened to REST. REST is so popular that it's generally considered the standard protocol for web APIs.

So, why do so many developers prefer REST other options like RPC, SOAP, or COBRA? Chiefly it's down to how easy REST APIs are for developers to understand and implement because they use standard HTTP requests.

At the time of writing, ProgrammableWeb, a news source dedicated to information about the Web as a programmable platform, lists almost 24,500 APIs. There's an API for everything from Google Maps to NASA's "Astronomy picture of the day" to an API that sends insults. If you can think it up, there's probably an API for it.

Examples of APIs

Travel booking - Sites like com and booking.com use APIs to aggregate thousands of flights and destination options from various providers.
Twitter bots - If you've spent any time on Twitter, you've probably encountered the numerous bots that use the Twitter API to conduct automated tasks. For example, the Netflix Bot tweets every time new content has been added to the streaming service. The Grammar Bot corrects misuse of grammar on Twitter.
PayPal - You'll see "Pay with PayPal" embedded on many websites that take payments, like Airbnb, eBay, and various ecommerce sites.

What is a Webhook?

You can think of a webhook as an API driven by events instead of requests. Webhooks are a way for apps to send automated messages or other information to other apps when an event occurs. So, when something changes in the source app, the webhook broadcasts this new information immediately. A simple way to think of it is as a notification from one system to another about an event that just happened.

You might see webhooks called "reverse APIs." This is because the communication is initiated by the app sending the data instead of the one receiving it.

Webhooks are more lightweight and resource-efficient than their API cousins, which is why they've been quickly gaining popularity in recent years.

Examples of Webhooks

Mailchimp offers webhooks that allow you to alert your application when a campaign has finished, detect when an email starts bouncing, and more.
Shopify offers webhooks so you can receive notifications about events happening in your shop. For example, a webhook could trigger an action when a customer creates a cart.
Dropbox offers webhooks so you can get real-time information about file changes in Dropbox.

A more general example of a webhook would be events that happen on a payment gateway. For example, you might receive a notification from a service like PayPal or Stripe when a payment is made, the payment fails, or a subscription is canceled.

When To Use an API

APIs are excellent for scenarios with a constant change in data. Since APIs are more resource-intensive, it makes sense to use them when those resources will be well spent. For example, situations where new data is always available when the request comes in for the latest information.

However, you can use your resources more efficiently with APIs by imposing a call limit (limiting the number of calls you make in a given time frame). Still, you have to consider whether an API is genuinely the most appropriate choice or whether a webhook would be more suitable.

Additionally, you might want to use an API because the application you wish to communicate with doesn't support webhook integrations or because you want to make a change based on the information you receive (something webhooks aren't capable of because they strictly notify).

When To Use a Webhook

While APIs have long been the golden standard for sharing information between systems, they're not always the most appropriate choice for every scenario due to their resource-heavy nature. Additionally, more minor requests and tasks don't need the added functionality that comes with APIs.

With that in mind, webhooks are most suitable for scenarios where you want a messenger for smaller data. It can also be ideal for situations where you want to display real-time data on your app or platform but don't want to use an API because this data is slow to change. For example, an API is more suitable for real-time weather updates because the weather can change quickly, and people make real-world decisions based on weather conditions. However, if you wanted your app to display how many weeks into the year we are, a webhook might be more suitable. There's no use wasting resources to continually ask, "What's the current week number?" when it's going to be "10" every day for a week.

Another reason to use a webhook is if there's no API currently available to do the job or it's faulty.

Webhooks also have a few disadvantages that could sway you to opt for an API if you find them sufficiently risky. For example, consider what happens if your source app goes offline. You'd miss potentially critical updates, but you might not know until a suspicious amount of time has passed. Additionally, since you can't control data flow with webhooks, you might find that your system gets overwhelmed with updates.

What's the Verdict?

When it comes to webhooks vs. APIs, it's not a case of which one is objectively better, but rather which is more suitable for what you want to do. As a result, you'll likely find that most large applications will use a combination of APIs and webhooks together to communicate effectively.

[1] https://nordicapis.com/apis-have-taken-over-software-development/