A webhook is an HTTP callback mechanism that enables one application to notify another in real time when a specific event occurs. Rather than requiring a system to repeatedly poll an API for updates, a webhook delivers data automatically to a configured endpoint URL at the moment an event takes place — making it a foundational pattern in modern application integration and event-driven architecture.
When a defined event is triggered in a source system, that system constructs an HTTP POST request containing a structured payload describing the event and sends it to the receiving application's endpoint. The receiving application processes the payload and responds accordingly, without any manual intervention or scheduled polling.
Webhooks are used across virtually every category of software development — from payment processing and version control to CRM updates, form submissions and infrastructure monitoring — wherever real-time, automated communication between systems is required.
What is a Webhook?
A webhook is a server-to-server HTTP request initiated by a source application when a predefined event occurs. Unlike a traditional API call where the client requests data on demand, a webhook inverts this relationship: the source system pushes data to the destination as soon as the event happens, without the destination needing to ask for it.
The destination is a publicly accessible URL — the webhook endpoint — hosted by the receiving application. When the source fires the webhook, it sends an HTTP POST request to this URL containing a payload, typically formatted as JSON, that describes the event and includes relevant data. The endpoint receives the request, processes the payload and returns an HTTP response to acknowledge receipt.
Webhooks are sometimes referred to as reverse APIs or push APIs. They are the standard mechanism by which platforms such as Stripe, GitHub, Shopify and Twilio notify external systems of events, and form the backbone of most workflow automation and integration platforms.
Key Features and Capabilities
- Event-driven delivery: Payloads are pushed to the endpoint immediately when a triggering event occurs, eliminating the need for polling and reducing latency.
- HTTP POST with structured payloads: Data is delivered as a standard HTTP request, typically with a JSON body, making it compatible with any web framework or language.
- Event type filtering: Most webhook providers allow configuration of which specific events should trigger delivery, avoiding unnecessary traffic to the endpoint.
- Signature verification: Providers typically sign webhook payloads with a secret key using HMAC, enabling the receiving application to verify that requests are authentic and have not been tampered with.
- Delivery status and retry logic: Failed deliveries — where the endpoint returns a non-2xx response or times out — are automatically retried by the provider according to a defined schedule.
- Delivery logs and inspection: Most providers maintain a log of webhook attempts, including request and response details, to support debugging and auditing.
- Custom headers: Additional metadata such as API version, event type or authentication tokens can be included in request headers alongside the payload.
- Endpoint registration via API or UI: Webhook destinations can be registered and managed programmatically through the provider's API or through a configuration interface.
How Webhooks Are Typically Used in Development and Automation
Payment processing is one of the most well-established webhook use cases. When a customer completes a payment, a provider such as Stripe fires a webhook to the application's endpoint. The application receives the event, updates the order status, triggers fulfilment and sends a confirmation — all without polling the payment API. The same pattern handles failed payments, refunds, subscription renewals and dispute events.
Version control and CI/CD pipelines rely heavily on webhooks. A push to a repository on GitHub or GitLab fires a webhook to a CI server, triggering a build, test run or deployment pipeline. Pull request events, merge completions and release publications are similarly propagated to downstream tooling — chat notifications, project management updates or deployment systems — via webhook.
Workflow automation platforms such as Zapier, Make and n8n use webhooks as a primary trigger type, enabling third-party applications that lack native integrations to initiate automated sequences by posting to a platform-generated endpoint URL. This makes webhooks a universal entry point for connecting disparate systems.
Infrastructure and monitoring tools use webhooks to route alerts and status changes to incident management systems, on-call platforms or communication channels. When a threshold is breached or a service goes down, a webhook fires immediately — pushing the event into the relevant workflow without delay.
Who Webhooks Are Best Suited For
Backend and integration developers building event-driven systems will encounter webhooks as a standard requirement when connecting to any major SaaS platform. Understanding how to receive, validate and process webhook payloads is a core skill for working with payment APIs, version control platforms, CRMs and communication services.
Platform engineers and DevOps practitioners use webhooks to wire together CI/CD pipelines, monitoring systems and incident response workflows, enabling automated reactions to infrastructure and deployment events without manual polling or intervention.
Teams building integration middleware, internal tooling or automation pipelines will often expose webhook endpoints as the primary mechanism for ingesting events from external systems, treating them as the real-time data entry point for downstream processing logic.
No-code and low-code practitioners use webhook triggers extensively within automation platforms, connecting services that lack direct integrations by routing events through webhook URLs into structured workflows.
Deployment, Access and Integrations
A webhook endpoint is simply an HTTP route exposed by the receiving application, implemented in any web framework or language. The endpoint must be publicly accessible over HTTPS, accept POST requests and return a 2xx response promptly upon receipt — deferring any heavy processing to an asynchronous queue to avoid timeout-related delivery failures.
During local development, tools such as ngrok, localtunnel or the Stripe CLI can expose a local server to the internet, allowing webhook payloads from external providers to reach a development environment without deploying to a public host.
Providers register webhook endpoints via their developer dashboard or management API, where event type subscriptions, signing secrets and retry policies are also configured. Webhook functionality is supported natively by most major platforms — including Stripe, GitHub, Shopify, Twilio, HubSpot, Salesforce and PagerDuty — and is a standard trigger and action type in all major workflow automation tools.
Summary
A webhook is an HTTP POST request sent by a source application to a configured endpoint URL when a specific event occurs, delivering structured event data in real time without the need for polling. It is the standard mechanism for event-driven integration between web applications, enabling immediate, automated communication across services at the moment something happens.
Implemented as a publicly accessible HTTPS endpoint in the receiving application, webhooks are compatible with any web framework and integrate natively with virtually every major SaaS platform and automation tool. Correct implementation requires prompt acknowledgement of receipt, asynchronous processing, payload signature verification and idempotent event handling — practices that together ensure reliable, secure and efficient event-driven integration.
Example workflow
An inbound webhook triggers the connected automation instantly. No manual work.
Frequently asked questions
What is the difference between a webhook and a REST API call?
A REST API call is initiated by the client, which requests data from the server on demand. A webhook inverts this: the server initiates the request and pushes data to the client when an event occurs. API calls are pull-based; webhooks are push-based. Webhooks are more efficient for event-driven scenarios where the client would otherwise need to poll repeatedly to detect changes.
How do I verify that a webhook request is authentic?
Most providers sign webhook payloads using HMAC with a shared secret. The signature is included in a request header. On receipt, your endpoint recomputes the signature using the raw request body and your secret, then compares it to the value in the header. If they match, the request is authentic. Never skip signature verification on production endpoints — without it, any party that knows your endpoint URL can send arbitrary payloads.
What should my endpoint return in response to a webhook?
Return a 2xx HTTP status code as quickly as possible to acknowledge receipt. Processing the payload — updating databases, triggering further actions — should happen asynchronously after the response is sent. If your endpoint takes too long to respond, the provider may consider the delivery a failure and trigger a retry, potentially resulting in duplicate processing.
How should I handle duplicate webhook deliveries?
Webhook providers may deliver the same event more than once, particularly after a retry. Design your endpoint to be idempotent — processing the same event multiple times should produce the same outcome as processing it once. Use the unique event ID included in the payload to detect and discard duplicates by checking against previously processed IDs stored in a database or cache.
How do I test webhooks during local development?
Use a tunnelling tool such as ngrok or localtunnel to expose your local server via a public HTTPS URL, then register that URL as the webhook endpoint with your provider. Some providers, such as Stripe, also offer CLI tools that forward webhook events directly to a local server without requiring a tunnel. Webhook inspection tools such as Webhook.site allow you to capture and examine raw payloads before writing any handling code.
What happens if my endpoint is down when a webhook is fired?
If your endpoint returns a non-2xx response or fails to respond within the provider's timeout window, the delivery is marked as failed and the provider will retry according to its retry schedule — typically with exponential backoff over a period of hours or days. After the maximum retry attempts are exhausted, the event is usually dropped. Monitor delivery logs regularly and implement alerting for sustained delivery failures to avoid silently missing events.
