Webhook

Webhook is an automated mechanism that sends real-time HTTP notifications from one application to another when specific events occur, enabling event-driven communication between systems. Unlike traditional APIs where clients must repeatedly poll servers for updates, webhooks use a "push" model where the source system automatically delivers data to a predetermined endpoint URL whenever triggered events happen. This approach enables instant data synchronization, workflow automation, and real-time integrations across web services, making webhooks essential for modern application architectures and data pipelines.

Also known as: Web callback, HTTP callback, reverse API, push notification, event-driven notification

Comparisons

• Webhook vs. API Polling: API polling requires clients to repeatedly request updates at intervals, while webhooks automatically push data when events occur, reducing unnecessary network traffic and improving real-time responsiveness.
• Webhook vs. WebSockets: WebSockets maintain persistent bidirectional connections for continuous communication, whereas webhooks establish temporary connections only when events trigger notifications.
• Webhook vs. Message Queue: Message queues provide reliable asynchronous communication with delivery guarantees and buffering, while webhooks offer simpler direct HTTP-based event notifications without intermediate brokers.

Pros

• Real-time updates: Delivers instant notifications when events occur, eliminating polling delays and enabling immediate responses to system changes or user actions.
• Resource efficiency: Reduces server load and network bandwidth by sending data only when necessary, rather than processing constant polling requests that return no new information.
• Simple implementation: Straightforward HTTP-based mechanism requires minimal infrastructure—just an accessible endpoint URL to receive POST requests with event data.
• Scalable integration: Enables loosely coupled system architectures where applications can communicate without tight dependencies or constant connection maintenance.

Cons

• Delivery reliability: No guaranteed delivery mechanism—if the receiving endpoint is down or unreachable, webhook notifications may be lost without built-in retry logic.
• Security considerations: Exposed endpoints require proper authentication, validation, and rate limiting to prevent unauthorized access, data injection, or denial-of-service attacks.
• Debugging complexity: Asynchronous nature and external triggering make webhook-based workflows harder to test, debug, and trace compared to synchronous API calls.

Example

An e-commerce analytics platform monitors competitor pricing changes by integrating with a web scraper API service that provides webhook notifications. Instead of constantly polling for updates, they configure the scraping service to send webhook notifications whenever product prices change on monitored websites. When the scraper detects a price drop using residential proxies, it immediately sends an HTTP POST request to the analytics platform's webhook endpoint with the updated pricing data. The platform processes this real-time notification through their data pipeline, triggers pricing alerts to clients, and updates their competitive intelligence dashboard—all within seconds of the actual price change occurring on the competitor's website.