What is the difference between webhooks and APIs?

Webhooks and APIs are both used to enable communication and data exchange between systems, but they differ in their functionality and implementation.

Think of an API as a menu at a restaurant. You can pick and choose what you want from the selection and the kitchen (computer system) will complete your order. While a webhook is like a waiter who comes to update you as soon as your order is ready, without you having to use a menu or keeping a tab on your order. Webhooks are event-driven notifications that push data from one system to another in real-time, while APIs provide a request-driven mechanism for clients to retrieve or manipulate data from a server.

Webhooks are suitable for real-time updates and one-way communication, whereas APIs support both one-way and two-way communication, making them more flexible but requiring polling or manual requests.

Trigger Mechanism

• Webhook: A webhook is a way for one system to provide real-time notifications or event data to another system. It relies on an event-driven architecture, where the receiving system is notified only when a specific event or trigger occurs.
• API: An API (Application Programming Interface) is a set of rules and protocols that allows different software applications to communicate with each other. APIs are generally request-driven, meaning the client initiates the request to the server to retrieve or manipulate data.

Communication Direction

• Webhook: Webhooks are typically used for one-way communication. When an event occurs in the source system (a booking is created), it sends a request to the predefined URL (endpoint) of the receiving system, which then processes the incoming data.
• API: APIs support both one-way and two-way communication. Clients can send requests to the server to retrieve or modify data, and the server responds with the requested data or performs the requested action.

Data Flow

• Webhook: Webhooks transfer data as an HTTP POST request to the specified endpoint. The data payload (JSON format) usually contains information about the event that triggered the webhook. The receiving system processes this data and takes appropriate actions.
• API: APIs provide a structured and well-defined way to interact with a system. Clients can send requests using different HTTP methods (GET, POST, PUT, DELETE) and receive responses in a predefined data format (such as JSON or XML) containing the requested data or information about the success/failure of the operation.

Real-Time vs. Polling

• Webhook: Webhooks are ideal for real-time or near real-time updates. The receiving system is notified instantly when the event occurs, eliminating the need for continuous polling or frequent manual requests.
• API: APIs require the client to periodically poll or send requests to the server to retrieve new data. The frequency and timing of data retrieval depend on the client’s needs, but it can result in additional overhead and delays if real-time updates are required.

Implementation Complexity

• Webhook: Implementing a webhook typically involves setting up an endpoint URL on the receiving system to receive incoming requests. The receiving system needs to handle and process the incoming data appropriately.
• API: Implementing an API involves defining endpoints, request/response structures, and authentication mechanisms. Both the server and client sides need to be developed and maintained to support the API.