What is API?

An API (Application Programming Interface) is a set of rules and tools that lets different software programs talk to each other. Think of it as a menu in a restaurant: the menu lists what you can order, and the kitchen (the software) knows how to prepare it. The API tells developers what requests they can make, what data they can send, and what responses they’ll get back.

Let's break it down

  • Endpoint: A specific URL where a request is sent (e.g., https://api.example.com/users).
  • Request: The message you send to the endpoint, usually including a method like GET (read data) or POST (send data).
  • Response: The data the server sends back, often in JSON or XML format.
  • Authentication: A way to prove who you are, such as an API key or OAuth token.
  • Rate limits: Rules that limit how many requests you can make in a certain time period to protect the server.

Why does it matter?

APIs let different apps work together without sharing all their internal code. This makes it easier to build new features, integrate services (like payment processing or maps), and keep systems modular. For developers, APIs speed up development because they can reuse existing functionality instead of building everything from scratch.

Where is it used?

  • Mobile apps calling a backend server for data (e.g., a weather app fetching forecasts).
  • Websites pulling social media feeds, payment gateways, or video streams.
  • Smart home devices communicating with cloud services.
  • Business systems linking inventory, shipping, and accounting software.
  • Public data portals offering open data (e.g., government statistics).

Good things about it

  • Reusability: One API can serve many different applications.
  • Scalability: Services can grow independently; the front‑end can change without touching the back‑end.
  • Speed: Developers can add features quickly by using third‑party APIs.
  • Standardization: Common protocols (HTTP, REST, GraphQL) make learning and integration easier.
  • Security: Proper authentication isolates internal systems from direct access.

Not-so-good things

  • Dependency risk: If an external API changes or goes down, your app can break.
  • Rate limits: Too many requests may be blocked, requiring careful planning.
  • Complexity: Managing multiple APIs, versions, and authentication can become tangled.
  • Performance: Network latency adds delay compared to local function calls.
  • Security concerns: Exposing APIs can open attack vectors if not properly secured.