What are webhooks?

Webhooks let applications send real-time data automatically when an event occurs. One system notifies another instantly via an HTTP request rather than repeatedly polling the API for updates. This guide explains how webhooks work, their key components, and how teams use them to automate workflows and integrate with other apps.

What are webhooks

A webhook is a way for one application to automatically send data to another application when something changes in the system. The sending system immediately delivers the information as soon as the change occurs, instead of repeatedly requesting updates via API calls.

Technically, a webhook works as an HTTP request, most often a POST request, sent to a predefined HTTP endpoint (URL). The request includes a payload, usually formatted in JSON, that contains details about what occurred.

Once configured, the sending system automatically delivers this data to the receiving system. The receiving end server processes the payload and returns an appropriate response, such as an HTTP status code 200 OK, to confirm the request was successfully received.

A common example is online payments. When a customer completes a payment through a payment app, the app can send a webhook to another application with the transaction details. The receiving system can then automatically update the order status, generate an invoice, or send a confirmation email without requiring manual checks.

How webhooks are different from API polling

Historically, applications handled the above process by issuing repeated HTTP requests to retrieve data from other systems. This API polling method increased server load, consumed unnecessary resources, and caused delays, making it hard to keep real-time integrations running smoothly at scale.

Webhooks address this challenge by shifting the responsibility to the source system. The source application sends a webhook to a pre-defined URL when an event occurs. This sends real-time data as soon as it becomes available. This push-based model, sometimes called a reverse API, enables real-time notifications, faster downstream processing, and better service integration.

Because of this efficiency, webhooks are widely used for payment processing, workflow automation, monitoring alerts, and integrations between modern applications.

Key components of webhooks

Webhooks rely on a few essential parts to function properly. Understanding these components helps clarify how webhooks send real-time event data between systems and trigger actions across applications.

1. Event source (triggering system)

The event source is the application or service in which a change occurs. It monitors system activity and sends a webhook when a relevant event occurs.

Examples of event sources include payment platforms, e-commerce systems, or CRM tools. For example, an online store detecting a completed order can act as the event source that sends a webhook.

2. Event

An event is the specific action or change that occurs inside the event source. When this action happens, it signals the system to send webhook data.

Examples of events include: a new order is created, a payment is completed, a user registers, and a file is uploaded. Each event carries information that the receiving application can process.

3. Webhook endpoint (Destination URL)

The webhook endpoint is a specific URL provided by the receiving system. It acts like a mailbox address where the webhook’s data gets delivered. Once an event happens, the event source sends an HTTP request (usually a POST) to this endpoint.

4. Event payload (Data)

The payload is the data package sent from the event source to the webhook endpoint. It contains structured information about the event, such as user details or order information, typically formatted in JSON (or sometimes XML). This payload gives the receiving system the context it needs to take action.

5. Subscriber or listener

A subscriber (also called a listener) is the application or service that receives and processes the webhook data at the endpoint. Once the listener receives the payload, it determines what to do with it, such as updating a database, triggering automation, or sending a notification.

6. HTTP Request and response

Webhooks operate over standard HTTP requests:

• The event source sends an HTTP request to the webhook endpoint.
• The listener replies with a status code (like 200 OK) to confirm receipt.

This request-response flow ensures the webhook is acknowledged and processed correctly.

7. Security ;ayer

Since webhooks deliver data over the web, security mechanisms are critical. Secret keys or signatures can validate that the webhook request is authentic. HTTPS encryption ensures data stays private during transit. These measures help protect against spoofed or malicious webhook requests.

8. Delivery & retry mechanism

Most webhook systems include mechanisms to ensure reliable delivery:

• Retries: If a webhook fails to deliver, the source may retry sending.
• Status tracking: Systems log deliveries and response statuses to help with debugging and reliability.

How webhooks work

Here’s how the process typically works from start to finish:

1. A webhook endpoint is registered. The receiving application provides a unique URL (called a webhook endpoint) to the sending application. It specifies which events it wants to listen for, such as payment completed, user created, or job finished.
2. An event occurs in the source system. When the predefined event happens in the source application, it prepares data related to that event.
3. The source sends an HTTP request. The source application sends an HTTP request, most commonly a POST request, to the registered webhook URL. It includes a payload (usually in JSON, XML, or form-encoded) that describes what just happened.
4. The destination receives and processes the data. The receiving system accepts the request, verifies it, and takes action such as triggering a workflow, updating a database, sending a notification, or launching automation.
5. A response is returned. The destination typically responds with an HTTP status code (like 200 OK) to confirm successful receipt. If something goes wrong, error codes (such as 404 or 500) may be returned, prompting retries. This entire exchange happens automatically and in near real-time.

Benefits of using webhooks

Webhooks improve how applications communicate and automate tasks. Here are some of their main benefits:

Real-time data updates

Webhooks send data the moment an event occurs, keeping systems synchronized without delays. When a customer completes a payment, a webhook instantly updates the CRM and accounting software and sends a confirmation email - no waiting, no refresh.

Lightweight payloads

Webhooks are designed to send small, focused payloads rather than large datasets. The server determines what information is included in the request, while the receiving system interprets the payload and decides how to use it.

Because the client does not control the timing or size of the transfer, webhook messages usually contain only the essential event data, often acting as a notification that something changed between two systems.

Workflow automation

Webhooks allow for automated communication between apps, eliminating manual intervention. A new lead form submission triggers a webhook that adds the lead to a CRM, assigns it to a sales rep, and automatically sends a welcome email.

Increased efficiency & reduced manual work

By replacing manual data entry and API polling, webhooks help teams work faster with fewer errors. They provide a more efficient way to share data between applications, improving overall system performance. Instead of checking every hour for new support tickets, a webhook pushes ticket data instantly to a Slack channel for immediate action.

Customization & flexibility

Webhooks let you choose exactly which events trigger data transfers, giving complete control over integrations. An e-commerce platform triggers webhooks only for high-value orders, launching fraud checks or priority fulfillment workflows.

Easy integration with third-party apps

Webhooks connect tools that may not have native integrations, expanding automation possibilities. A marketing tool sends webhook data to a custom analytics dashboard whenever a campaign is launched or paused.

Scalability & reliability

Webhooks scale as event volume grows and work reliably with proper retry and async handling. During a flash sale, thousands of order events trigger webhooks that queue data for background processing without slowing down the website.

Simple setup

Webhooks use standard HTTP, making them faster and easier to implement than complex integrations. A developer can register a webhook URL in minutes and start receiving user activity events without building a full API integration.

Use cases for webhooks

By turning events into automated actions, webhooks support a wide range of use cases from system integrations to event-driven automation. Below are some of the most common and practical use cases for webhooks.

Monitoring and incident management

In many environments, monitoring and observability tools detect system events like infrastructure failures, security alerts, or application performance issues. When these tools detect a condition, they can send a webhook to an automation platform. The webhook acts as a trigger that launches automated responses, such as creating incident tickets, restarting services, scaling infrastructure, or applying configuration fixes. They reduce downtime by enabling proactive issue resolution.

Infrastructure automation and workflow automation

Webhooks automate infrastructure tasks, such as deploying updates. They can be integrated with other tools and services, such as GitHub or Jenkins.

In many teams, infrastructure is managed using Infrastructure as Code (IaC), where configuration files define servers, networks, and other resources. When developers push code changes to a Git repository, the repository can send a webhook notification to an automation platform.

Used for event-driven automation

Webhooks can automate event-driven processes, enabling apps to respond quickly to specific events. They can be used to trigger actions in response to changes or updates, such as sending notifications or updating data. Webhooks can be used to integrate with other tools and services, such as Zapier or IFTTT. By connecting monitoring systems with automation workflows, webhooks help organizations reduce mean time to resolution (MTTR) and maintain system reliability with minimal manual intervention.

Real-time notifications

Webhooks send instant alerts when important events take place. They can notify users or teams through email, chat tools, or dashboards. Webhooks ensure critical updates are delivered without delays. They are widely used for order updates, system alerts, and user activity notifications.

Data integration

Webhooks enable seamless data exchange between multiple systems. They keep data synchronized across platforms in real-time. Webhooks eliminate the need for manual data transfers or periodic syncing. They are often used to integrate CRMs, analytics tools, and marketing platforms.

Best practices for building and implementing webhooks

Below are the key best practices you should follow when building and implementing webhooks.

Creating a new webhook

To create a new webhook, define the event that triggers it and the data it sends. You will need to specify the webhook endpoint, which is the URL that will receive the HTTP request. You can use tools like GitHub or other web services to create and manage webhooks. Make sure to test your webhook to ensure it is working correctly and receiving data as expected. Use version control to track changes and updates to the webhook code.

Testing and verification

Testing webhooks is crucial to ensure they work correctly and receive data as expected. Make sure to verify the webhook request's signature to ensure it comes from a trusted source. Test your webhook across different scenarios to ensure it works as expected. Implement proper error handling and logging to ensure issues are detected and resolved quickly.

Security considerations

Webhooks require proper security measures to prevent unauthorized access or data breaches. Webhook endpoints are publicly accessible URLs, so security is essential. Standard protection methods include:

• Secret keys or signatures to verify authenticity
• HMAC-based signature validation
• HTTPS and TLS encryption
• Mutual Transport Layer Security (mTLS) for high-security environments

Each incoming request should be verified before processing to prevent spoofing or abuse.

• Use HTTPS to encrypt data sent between applications and verify the sender's identity.
• Implement signature verification to ensure the webhook request comes from a trusted source.
• Use secure storage to store sensitive data, such as API keys or access tokens.

Delivery, reliability, and processing considerations

Webhooks are designed for speed, but they come with essential implementation considerations:

• At least once delivery - Webhooks may be sent more than once. Systems must be idempotent, meaning duplicate events don’t cause issues.
• No guaranteed order - Events may arrive out of sequence. Timestamps in payloads help determine relevance.
• Throughput spikes - Webhooks are not rate-limited by default. Storing incoming events in a queue before processing helps avoid data loss.
• Timeouts - Because webhook providers expect fast responses, long-running tasks should never block the request.

Common challenges and solutions

While webhooks are powerful and efficient, they come with a few common challenges. The good news is that most of these issues are well-known and easy to fix when handled correctly. Below are the most frequent webhook challenges and how to solve them.

Duplicate Events

Webhooks are often used with at-least-once delivery, which means the same event can be sent more than once. This can cause duplicate records or repeated actions.

Solution: Make your webhook processing idempotent. Use unique event IDs or timestamps to check if an event has already been processed before taking action.

Failed or Missed Deliveries

If the receiving server is down or slow, webhook requests may fail or time out.

Solution: Always return a fast 200 OK response. Use retry mechanisms on the sender side. Store incoming events in a queue and process them later

Short Timeouts

Most webhook providers wait only 1–5 seconds for a response. Long processing can cause failures.

Solution: Use asynchronous processing. Acknowledge the webhook immediately, then handle heavy tasks (like database updates or API calls) in the background.

Security Risks

Webhook endpoints are public URLs and can be targeted by fake or malicious requests.

Solution: Verify webhook signatures using secret keys. Use HTTPS for encrypted communication. Reject requests that fail authentication

High Traffic and Load Spikes

During peak events (sales, deployments, alerts), a system may receive thousands of webhook requests at once.

Solution: Use message queues (like Kafka or SQS). Rate-limit processing, not delivery. Scale webhook handlers horizontally. This helps your system handle traffic without crashing.

Out-of-Order Events

Webhooks are not guaranteed to arrive in the correct order.

Solution: Use timestamps or sequence numbers in the payload to identify stale or outdated events and ignore them when needed.

Difficult Debugging

If something breaks, it’s hard to know whether the issue is on the sender's or the receiver's side.

Solution: Log all incoming webhook requests. Track response status codes. Use webhook testing and inspection tools. Good logging makes troubleshooting much easier.

Version Changes in Payloads

Webhook providers may update payload formats, which can break existing integrations.

Solution: Build backward-compatible parsing. Avoid hard dependencies on exact payload structure. Monitor provider changelogs. This keeps integrations stable over time.

Wrapping up

Webhooks deliver real-time events across systems, but in production, they often stop at delivery. Teams still need to interpret what changed, understand the context, and decide on an action. This gap between event notification and meaningful action is where many webhook-driven workflows fall short. This is where Glean stands apart.

Glean connects to all your enterprise applications through 100+ out-of-the-box connectors, continuously syncing data and permissions in real-time. When webhook-driven events occur, such as updates in source systems, documents, or workflows, Glean understands those changes in the context of your company’s knowledge, access controls, and ongoing work.

With actions and triggers, teams can move from understanding to execution using natural language. Employees can describe what they want to do, combine events or schedules with actions, and safely automate work, without building fragile pipelines or writing custom glue code.

Rather than treating webhooks as isolated technical signals, Glean turns them into enterprise-ready intelligence and controlled action. This approach preserves human oversight, respects permissions, and ensures automation remains trustworthy and aligned with business intent.

FAQs

What is the purpose of a webhook?

The purpose of a webhook is to automatically send data when an event occurs. It allows one application to instantly notify another, enabling real-time actions without waiting or manual checks.

What is the difference between API and webhook?

An API requires a system to request data (pull). A webhook sends data automatically when something changes (push). In simple terms, APIs ask for information, while webhooks deliver it automatically.

What triggers a webhook?

A webhook is triggered by a specific event, such as a new user signing up, a payment being completed, a file being uploaded, or a status or data change. When the event occurs, the webhook sends data immediately.

What is a webhook for dummies?

A webhook is like a doorbell for apps. Instead of checking repeatedly to see if something happened, one app rings the bell (sends data) as soon as the event occurs.

What is an example of a webhook?

When someone fills out a contact form on a website, a webhook sends their details to a CRM or email tool instantly, without manual export or refresh.

Is a webhook just a URL?

No. A webhook uses a URL and includes an event trigger, a data payload, an HTTP request, and security verification.

Is a webhook a REST API?

No. A webhook is not a REST API, but it works with APIs. APIs let you request data, while webhooks send data automatically when an event happens.

When should you use webhooks?

You should use webhooks when you need real-time updates, avoid polling, automate workflows, and need your systems to react instantly to events

What are some alternatives to webhooks?

Common alternatives include API polling (checking repeatedly for updates), WebSockets (two-way real-time communication), message queues, and Pub/Sub systems. Each has different use cases depending on scale and complexity.

Are webhooks secure?

Yes, if implemented correctly. Security measures include HTTPS, secret keys, and signature verification to ensure requests are trusted and not tampered with.

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