What is API (Application Programming Interface)?
Turkish: API
An API is a contract that lets software systems request approved data or actions from one another through documented endpoints.
What is an API?
API (Application Programming Interface) is the interface that defines what data or actions a software system exposes, under which rules, and in which format. A user interface is for people; an API is the agreed entry point for software-to-software communication.
For example, an e-commerce site that needs a shipping label does not connect directly to a carrier’s database. It sends a request to the carrier API, authenticates itself, and receives a tracking number or an error response, often as JSON.
How Does an API Work?
- Client: The application requesting data or an action
- Endpoint: The URL or operation name the request is sent to
- Authorization: Access control through an API key, OAuth2 token, or similar mechanism
- Server: The system that validates, processes, and answers the request
- Response: Usually JSON; sometimes XML, a file, or a stream
Types of APIs
- REST API: A common approach based on HTTP methods and resource URLs
- GraphQL: A query model where clients request the fields they need
- SOAP: An XML-based protocol still found in enterprise integrations
- WebSocket: A persistent connection for real-time two-way messaging
- Webhook: An automatic callback sent when an event occurs
Business Use
APIs power payment collection, ERP and accounting connections, CRM synchronization, inventory-shipping flows, and mobile app backends. REST API design, webhook events, and secure API integration allow systems to work without manual file transfers.
In API development and integration projects, documentation, error handling, versioning, and monitoring matter as much as endpoint design.
Related Terms
API integration connects separate software systems so they can exchange data securely and keep workflows automated.
API GatewayAn API Gateway sits between clients and services to centralize routing, authentication, quotas, observability, and versioning.
API MarketplaceAn API marketplace combines API discovery, testing, subscriptions, pricing, documentation, and key management in one platform.
CDN (Content Delivery Network)A CDN caches static content on edge servers near users, reducing latency, bandwidth pressure, and load on the origin server.
Circuit BreakerThe circuit breaker pattern stops calls to failing dependencies temporarily, preventing cascading failures and wasted resources.
CORS (Cross-Origin Resource Sharing)CORS uses HTTP headers to tell browsers which origins may safely read responses from an API hosted on another origin.
EDI (Electronic Data Interchange)EDI lets companies exchange orders, invoices, shipment notices, and inventory messages between systems in standard formats.
ERP (Enterprise Resource Planning)ERP manages finance, inventory, sales, production, HR, and supply chain processes through a shared enterprise data model.
REST APIA REST API designs web services around resources and HTTP methods, making integrations predictable across web and mobile systems.
WebhookA webhook lets one system automatically send an HTTP request to another when an event occurs, so updates arrive without polling.