What is an API?

What is an API?

An API (Application Programming Interface) is a contract that allows software systems to communicate. It defines what requests can be made, how to make them, and what responses to expect.

• REST, GraphQL, gRPC, WebSocket, SOAP
• Powers every modern app — mobile, web, IoT
• Internal APIs connect microservices; external APIs serve third parties

GET    /api/users/1   -- return user
POST   /api/users     -- create user
PUT    /api/users/1   -- full update
PATCH  /api/users/1   -- partial update
DELETE /api/users/1   -- remove user