What's a Webhook?

September 11, 2023
Written by
SendGrid Team
Opinions expressed by Twilio contributors are their own
Reviewed by
Ayanna Julien
Opinions expressed by Twilio contributors are their own

What's a Webhook?

What are webhooks, and how can you use webhooks to push and pull data quickly in real-time? Below, we're answering these questions and more. This webhooks explained post will show you everything you need to know about webhooks, including what they are, how they work, examples, and how to get started.

A webhook is an API concept growing in popularity. As more and more of what we do on the web includes events, webhooks are becoming even more applicable. These are incredibly useful and a resource-light way to implement event reactions.

What is a webhook?

So what exactly is a webhook? By definition, a webhook (also called a web callback or HTTP push API) is a way for an app to provide other applications with real-time information. A webhook delivers data to other applications as it happens, meaning you get data immediately—unlike typical APIs where you would need to poll for data very frequently to get it in real-time.

Imagine a world where information flows effortlessly, like a symphony of harmonious data. A world where you don't have to constantly refresh your browser or send countless requests to fetch updates. Welcome to the realm of webhooks, where real-time communication dances to the beat of efficiency and automation.

This makes webhooks much more efficient for the provider and consumer. The only drawback to webhooks is the difficulty of initially setting them up.

Webhooks are sometimes referred to as reverse APIs because of the ability to give you what amounts to an API spec, and you must design an API for the webhook to use. The webhook will make an HTTP request to your app (typically a POST), and then you'll have to interpret it.

Webhooks vs. APIs: What's the difference?

Webhooks and APIs are both tools used in web development to enable communication between different software applications, but they serve different purposes and operate in distinct ways.

Here's a quick breakdown of the differences between webhooks and APIs:
  • Direction: Webhooks "push" data automatically based on events. APIs exchange data based on explicit requests in a "push" or "pull" process.
  • Trigger: Webhooks are event-driven, while APIs are request-driven.
  • Use cases: Webhooks are typically used for real-time notifications, while APIs handle a wide range of operations like data retrieval and updates.
  • Configuration: Webhooks need configuration for specific events and endpoints. APIs provide callable endpoints without event-based configuration.
  • Frequency: Webhooks operate in real time. APIs operate based on the frequency of requests.
  • Security: Webhooks push data to exposed endpoints, requiring security measures. APIs often demand authentication for data access.
While webhooks and APIs facilitate communication between applications, webhooks are event-driven and automatically send data when specific events occur—whereas APIs are request-driven and provide data or services in response to explicit requests.

The choice between using a webhook or an API depends on the specific needs and use cases of the application.

What are the benefits of webhooks?

Webhooks are the magical conduits that connect applications and systems, creating a seamless and synchronized orchestra of data exchange. They are the secret ingredient that brings harmony to the chaotic world of web development.

Here are a few of the most prevalent benefits of webhooks:
  • Real-time updates: Gone are the days of manual checks and tiresome refreshes. With webhooks, you can sit back and let the information come to you. Whether it's a new order on your e-commerce website or a notification from your favorite social media platform, webhooks ensure that you're always in the loop.
  • Automation: Webhooks trigger actions and unleash a cascade of events with the flick of a digital switch. Want to send a personalized email to a new subscriber? Webhooks make it happen. Need to update your CRM system when a customer makes a purchase? Webhooks have your back.
  • Integration: With webhooks, disparate systems become dance partners, seamlessly exchanging information and performing synchronized routines. Whether it's syncing data between different applications or bridging the gap between services, webhooks bring together the digital ensemble that powers our modern world.
  • Flexibility: Webhooks don't impose any constraints on the format or type of data they transmit. From humble JSON payloads to majestic XML documents, webhooks embrace them all. This flexibility empowers developers to craft custom-tailored solutions, opening the doors to endless possibilities and boundless creativity.
  • Security: Unlike their rowdy alternatives, webhooks are peaceful, patient listeners. They await their turn to receive the information they need, ensuring that your systems stay protected from unnecessary strain. By allowing you to define the endpoint where data is delivered, webhooks put you firmly in the driver's seat, giving you full control over the flow of information.

How do webhooks work?

Consuming a webhook

The first step in consuming a webhook is giving the webhook provider a URL to deliver a request. This is often done through a back-end panel or an API, meaning you also need to set up a URL in your app accessible from the public web.

Most webhooks will POST data to you in one of 2 ways: as JSON (typically) or XML (blech) to be interpreted, or as a form data (application/x-www-form-urlencoded or multipart/form-data). Either way, your provider will tell you how it delivers it (or even give you a choice in the matter). The good news is both of these are fairly easy to interpret, and most web frameworks will do the work for you. If the web frameworks don’t, you may need to call on a function or 2.

Debugging a webhook

Debugging a webhook can be complex at times, as webhooks are principally asynchronous. Thus, you must trigger them and wait, then check the response. This can be tiresome and is fairly inefficient. Luckily, there are better ways. It amounts to the following:
  1. Understand what the webhook provides by using a tool like RequestBin to collect the webhook’s requests.
  2. Mock the requests using a tool like cURL or Postman.
  3. Test the code on your machine by using a tool like ngrok.
  4. Watch the whole flow using a tool like Runscope.

Securing a webhook

As webhooks deliver data to publicly available URLs in your app, there’s the chance that someone else could find that URL and then provide you with false data. To prevent this from happening, you can employ a number of techniques. The easiest thing to do (and what you should implement before going any further) is to force TLS connections (HTTPS). Once you’ve implemented that, you may go forward and further secure your connection:
  1. The first, and most supported, way to secure a webhook is to add tokens to the URL that act as unique identification, e.g.,?auth=TK.
  2. The next option is to implement Basic Auth—this is also widely supported and very easy to do.
  3. The third option is to have the provider sign each request it makes to you and then verify the signature—unlike the first two solutions, which work great to prevent most attacks but have the disadvantage of sending the auth token with the request. This has the disadvantage of requiring the provider to have implemented request signing—meaning if it doesn't already, you’re probably out of luck.

Tips and best practices for creating webhooks

Here are a couple of things to keep in mind when creating webhook consumers:
  • Understand your webhook provider: Webhooks deliver data to your application and may stop paying attention after making a request. Meaning, if your application has an error, you'll lose your data. Many webhooks will pay attention to responses and resend requests if your application errors out. So if your application processed the request and still sent an error, there may be duplicate data in your app.
  • Check the scale of your webhook: Webhooks can make a lot of requests. If your provider has a lot of events to tell you about, it may end up issuing a distributed denial of service on your app. Make sure your application can handle the expected scale of your webhook. We made another tool, Loader.io, to help with that.
  • Implement security measures: As webhooks deliver data to publicly available URLs in your app, there's a risk of unauthorized access. Implement security measures like forcing TLS connections (HTTPS) for secure data transmission and adding tokens to the URL that act as unique identification.
  • Learn about data formats: Understand the data format your webhook will be sending. Most webhooks will POST data as JSON or XML. Ensure your application can interpret and process the data correctly.
  • Add rate limiting: Implement rate limiting to prevent abuse. This ensures that if there's a sudden spike in requests, your system won't be overwhelmed and crash.
  • Log and monitor events: Maintain logs of all webhook events and monitor them. This will help in troubleshooting issues and understanding the behavior of incoming requests.
  • Build robust documentation: If you're providing webhooks for other developers, ensure you have clear and comprehensive documentation. This should include details on how to set up the webhook, expected data formats, and how to handle different scenarios.

Try webhooks with Twilio SendGrid

The best way to truly understand a webhook is to try one. Luckily, Twilio SendGrid is here to help you get started learning how to use webhooks, including how to even parse emails through our webhooks. For more information on SendGrid's API, check out our docs pages.

Ready to start sending? Sign up for a Twilio SendGrid account to send 100 emails per day on our Free Forever plan.

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