What Are Webhooks
A webhook is an HTTP callback that automatically sends data from one application to another when a specific event occurs. That’s it. No scheduled checks, no repeated requests. Something happens, and the source system fires off an HTTP POST request to a URL you’ve registered.
The term was coined by Jeff Lindsay back in 2007. It stuck because it describes exactly what it does: a hook that works over the web.
Think of it as a reverse API. Instead of your application asking a server “did anything change?” over and over, the server tells you the moment something changes. The data arrives in a JSON payload, typically containing the event type, a timestamp, and whatever resource was affected.
Svix’s 2024 State of Webhooks report found that 85% of the top 100 API companies now offer webhooks, up from 83% the year before. Adoption of authentication best practices (specifically HMAC-SHA256 signatures) jumped by 17%.
That growth makes sense. The 2024 Gartner API Strategy Survey reported that 82% of organizations use APIs internally, while 71% also rely on third-party APIs from SaaS vendors. Webhooks sit right at the center of that. They’re the glue that makes API integration actually work in real time.
Stripe uses webhooks to notify your application when a payment succeeds. GitHub fires them when code gets pushed. Slack sends them when a message lands in a channel. Every major platform that connects with external systems relies on this pattern.
Without webhooks, you’d be stuck polling. And polling, well, it wastes resources and introduces delays. More on that in a moment.
How Webhooks Work
The mechanics are straightforward. An event happens inside a source system. That system sends an HTTP POST request to a callback URL you’ve configured ahead of time. Your server receives the request, processes the payload, and returns a status code.
That’s the full cycle. Five steps, usually completed in under a second.
The event trigger: Something changes. A customer makes a purchase on Shopify. A pull request gets merged on GitLab. A contact updates their email in HubSpot. Each of these is an event.
The HTTP POST: The source system constructs a request containing the event data and sends it to your registered endpoint URL. This happens server-to-server, no browser involved.
The payload: The request body carries structured data, almost always JSON. It includes the event type, a unique event ID, the timestamp, and the relevant resource data.
Your response: Your endpoint processes the incoming data and returns an HTTP 2xx status code. A 200 means “got it.” Anything outside the 2xx range, and most providers assume delivery failed.
Hookdeck’s 2025 webhook reliability research showed that delivery failure rates run between 3-5% when no retry logic exists. That might sound small, but at 100 events per day, you’re losing 3 to 5 events daily. At scale, that becomes thousands of missed signals.
Webhook Payloads and Headers
The payload is where the actual information lives. A typical JSON body from Stripe looks something like an object with a type field (say, paymentintent.succeeded), a created timestamp, and a nested data object containing the full resource.
Headers carry metadata. Content-Type is usually application/json. Most providers add a custom signature header for verification, like Stripe’s Stripe-Signature or GitHub’s X-Hub-Signature-256.
Payload sizes vary. Some providers send the full object (snapshot events), while others send thin payloads with just an ID and type, requiring you to fetch details via API. Stripe recently introduced thin events for high-volume scenarios to cut down on payload size.
If you’re working on the server side that handles these incoming requests, understanding back-end development patterns for asynchronous data handling becomes pretty relevant here.
Webhooks vs. APIs and Polling
This is where people get confused. Webhooks and APIs aren’t competing technologies. They’re different patterns for different problems.
| Pattern | Direction | Trigger | Best For |
|---|---|---|---|
| REST API | Pull (client requests) | On demand | Fetching data when you need it |
| Polling | Pull (repeated requests) | Scheduled interval | Systems without webhook support |
| Webhooks | Push (server sends) | Event-based | Real-time notifications |
| WebSockets | Bidirectional | Persistent connection | Live chat, streaming data |
Polling is the simplest to understand. Your application asks the server at regular intervals: “Anything new?” If nothing changed, you just burned a request for nothing. Multiply that across thousands of clients hitting an API every 30 seconds, and you’ve got a serious waste of bandwidth and compute.
Webhooks flip this. The server only talks when it has something to say. Zero wasted requests. Your system stays quiet until an event actually fires.
A RESTful API is pull-based by design. You send a GET request, you get data back. That works great when you need specific data on your schedule. But it falls apart when you need to react to changes the moment they happen.
WebSockets are a different animal. They maintain an open, bidirectional connection between client and server. Useful for live chat or real-time dashboards, but overkill for most event notification scenarios. And they carry more overhead in terms of infrastructure.
There are still times when polling beats webhooks. If the receiving system is unreliable or goes offline frequently, polling lets you catch up on missed data in bulk. Some software development processes also favor polling for batch operations where real-time delivery isn’t critical.
Stripe’s own documentation recommends using webhooks as the primary channel but implementing a backup polling job against the Events API for anything missed. That hybrid approach is what most production systems end up using.
Common Use Cases for Webhooks
Webhooks show up everywhere modern software systems need real-time data flow. Here’s where they matter most.
Payment processing: Stripe, PayPal, and Square use webhooks to notify your application when a charge succeeds, fails, or gets disputed. You can’t rely on synchronous payment confirmations alone because some payment methods take hours or days to resolve. Stripe processes over 8 billion API calls annually, and webhooks handle the asynchronous side of nearly all of those transactions.
CI/CD pipelines: GitHub and GitLab fire webhooks when code is pushed, pull requests are opened, or branches are merged. Those events trigger build pipelines that run tests, compile code, and deploy to staging environments. Without webhooks, continuous integration wouldn’t be continuous.
CRM synchronization: HubSpot and Salesforce send webhook notifications when contacts update, deals move stages, or new leads come in. This keeps your internal systems, marketing tools, and support platforms in sync without manual data entry.
E-commerce: Shopify fires webhooks for order creation, inventory updates, fulfillment status, and refunds. Shopify retries failed webhook deliveries up to 8 times over a 4-hour window before removing the subscription entirely.
Messaging and notifications: Slack and Discord use incoming webhooks for posting messages to channels from external systems. Twilio sends webhooks for SMS delivery receipts, call status updates, and voicemail transcriptions.
Automation platforms: Zapier and similar tools rely heavily on webhooks to connect applications that don’t have direct integrations. You set up a webhook trigger in one app, and it kicks off an automated workflow in another.
Gartner predicted that by 2025, over 90% of new enterprise applications would incorporate APIs as core components. Webhooks are a natural extension of that, because APIs need a push mechanism to keep connected systems in sync.
How to Set Up a Webhook
Setting up a webhook has two sides: the provider (the system sending events) and the consumer (your system receiving them). Most of the work is on the consumer side.
Step one: Create a publicly accessible HTTPS endpoint on your server. It needs to accept POST requests and parse JSON bodies. If you’re running locally during development, tools like ngrok or Cloudflare Tunnel can expose your localhost to the internet.
Step two: Register that URL in the provider’s webhook settings. Stripe, GitHub, Shopify, and most SaaS platforms have a dashboard where you paste your endpoint URL and select which event types to subscribe to.
Step three: Handle the initial verification. Some providers (like Meta and Slack) require a challenge-response handshake before they’ll start sending events. Others just start firing.
Step four: Test. Use the provider’s test event feature, or tools like Webhook.site and RequestBin, to inspect what payloads look like before writing any processing logic.
Took me a while to learn this, but the biggest mistake developers make here is trying to do too much inside the endpoint handler itself. Your endpoint should acknowledge the request fast, ideally under 200 milliseconds, and hand off actual processing to a background queue.
Webhook Endpoints in Practice
A production-ready webhook endpoint does three things fast: receive, validate, respond.
The handler reads the incoming HTTP POST body, verifies the signature (more on that in the security section), and returns a 200 status code. Actual business logic, like updating a database, sending a notification, or triggering a workflow, happens asynchronously.
Why? Because if your endpoint takes too long to respond, the provider assumes it failed and queues a retry. GitHub expects a response within 10 seconds. Stripe is more generous but will still flag slow endpoints.
If you’re working in a microservices architecture, webhook receivers often sit as lightweight services that do nothing but ingest events and push them onto a message queue like RabbitMQ or Amazon SQS. The actual processing happens downstream.
For teams using DevOps workflows, webhook endpoints often get deployed as serverless functions on AWS Lambda or Cloudflare Workers. They spin up on demand, handle the event, and shut down. No idle infrastructure.
Webhook Security
Webhooks are just HTTP requests. And any HTTP endpoint that’s publicly accessible can receive requests from anyone, not just the provider you’re expecting.
Without verification, an attacker could send fake webhook events to your endpoint and trigger actions like fulfilling orders, granting account access, or modifying records. This isn’t theoretical. It happens.
Signature Verification with HMAC
The standard approach is HMAC signature verification using SHA-256. Here’s how it works:
- The provider and your server share a secret key (generated during webhook setup)
- When the provider sends a webhook, it hashes the payload body using that secret and includes the resulting signature in a custom header
- Your server receives the request, computes its own hash of the payload using the same secret, and compares the two
- If they match, the request is authentic
Svix’s 2024 report showed a 17% increase in adoption of HMAC-SHA256 signatures among top API companies. Still, that means a significant number of implementations skip this step entirely. Not great.
Stripe, GitHub, Shopify, and most major providers all support this pattern. The header name varies (Stripe-Signature, X-Hub-Signature-256, X-Shopify-Hmac-SHA256), but the verification logic is the same.
Beyond Signatures
HTTPS: Your endpoint URL must use HTTPS. No exceptions. This encrypts data in transit and prevents man-in-the-middle attacks. Any serious provider will reject plain HTTP endpoints.
Timestamp validation: Include a timestamp in the signature check to block replay attacks. If the timestamp in the request is more than a few minutes old, reject it. Stripe includes a t parameter in their signature header specifically for this.
IP whitelisting: Some providers publish the IP ranges they send webhooks from. Adding those to an allowlist provides an extra layer beyond signature checks. This pairs well with a reverse proxy that filters incoming traffic before it reaches your application server.
If you skip signature verification and expose a webhook endpoint to the public internet, you’re basically inviting data injection. Implementing token-based authentication patterns alongside HMAC can add defense in depth, especially for sensitive financial or healthcare data.
For teams handling high-stakes data, it’s worth running your webhook security setup through a structured risk assessment matrix to map out what happens if verification fails or endpoints get compromised.
FAQ on What Are Webhooks
What is a webhook in simple terms?
A webhook is an automated HTTP callback that sends data from one application to another when a specific event occurs. Instead of your system repeatedly checking for updates, the source pushes a JSON payload to your endpoint URL instantly.
How are webhooks different from APIs?
APIs are pull-based. You request data when you need it. Webhooks are push-based, delivering data automatically when an event fires. Most software development projects use both together for complete server-to-server communication.
Are webhooks secure?
They can be, if you verify them properly. Providers like Stripe and GitHub include HMAC-SHA256 signatures in request headers. Your endpoint should validate every signature, use HTTPS, and check timestamps to prevent replay attacks.
What happens when a webhook delivery fails?
Most providers retry with exponential backoff. Stripe retries for up to three days. Shopify attempts eight retries over four hours. Without retry logic, failure rates sit around 3-5% according to Hookdeck’s 2025 research.
What is a webhook endpoint?
It’s a publicly accessible URL on your server that accepts incoming HTTP POST requests. The endpoint receives the event payload, processes it, and returns a 2xx status code. Keep your production environment endpoints fast, ideally responding under 200 milliseconds.
Can webhooks send data in formats other than JSON?
Yes, though JSON is the standard. Some systems use XML or form-encoded data. The Content-Type header tells your endpoint which format to expect. JSON dominates because it’s lightweight and easy to parse across languages.
What is webhook polling and why avoid it?
Polling means your application repeatedly asks a server for new data at set intervals. It wastes bandwidth when nothing has changed. Webhooks eliminate this by only firing when an actual event occurs, making real-time data synchronization far more efficient.
Which platforms support webhooks?
Stripe, GitHub, GitLab, Slack, Shopify, PayPal, Twilio, HubSpot, Salesforce, and Discord all support them. Svix’s 2024 report found 85% of top API companies offer webhooks. Zapier uses them as a core trigger mechanism for automation workflows.
How do I test webhooks during development?
Use ngrok or Cloudflare Tunnel to expose your localhost. Tools like Webhook.site and RequestBin let you inspect raw payloads without writing code. Stripe and GitHub also offer built-in test event features from their dashboards.
Do webhooks guarantee message delivery order?
No. Events can arrive out of sequence, and duplicate deliveries happen. Your webhook handler needs to be idempotent, processing the same event multiple times without side effects. Use event IDs to deduplicate and timestamps to handle ordering.
Conclusion
Webhooks are the push-based backbone of real-time communication between modern applications. Understanding what are webhooks gives you a clear advantage when building event-driven systems that connect platforms like Stripe, GitHub, Slack, and Shopify without wasting resources on constant polling.
The setup isn’t complicated. Register an endpoint, verify HMAC signatures, handle retries with exponential backoff, and keep your handler idempotent. That covers most production scenarios.
Where teams stumble is reliability. Build for failure from the start. Use message queues, log every delivery attempt, and implement dead letter handling for events that exhaust retries.
Whether you’re syncing CRM data, triggering continuous deployment pipelines, or processing payment notifications, webhooks cut the lag between event and action to near zero. Pair them with solid software scalability practices, and your system handles growth without breaking.
Get the fundamentals right. The rest follows.
Many of his resources are available on various design marketplaces and for free on Codepen.
Over the years, he's worked with a range of clients and contributed to design publications like Design Your Way, Designmodo, WebDesignerDepot, WPDean, Speckyboy, and Slider Revolution among others.
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