What is API?

An API, or 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 they can request, how to ask for it, and what they’ll get back.

Let's break it down

  • Endpoint: The specific URL where a request is sent (e.g., https://api.example.com/users).
  • Request: The message you send, usually containing a method (GET, POST, PUT, DELETE) and optional data.
  • Response: The data the server sends back, often in JSON or XML format.
  • Authentication: A way to prove who you are (API keys, tokens, OAuth) so the server knows you’re allowed to use the API.
  • Rate limits: Rules that limit how many requests you can make in a certain time to protect the service.

Why does it matter?

APIs let different apps and services work together without sharing all their internal code. This speeds up development, enables new features (like logging in with Google), and lets companies build ecosystems where third‑party developers can create add‑ons, integrations, and new products.

Where is it used?

  • Mobile apps fetching data from a server (weather, maps, social feeds).
  • Websites loading dynamic content (comments, product listings).
  • Cloud services connecting tools (e.g., Slack sending messages to a project‑management app).
  • IoT devices reporting sensor data to a central platform.
  • Payment gateways processing online transactions.

Good things about it

  • Reusability: Write code once, use it everywhere.
  • Scalability: Services can grow independently; the API stays the same.
  • Flexibility: Different platforms (web, mobile, desktop) can all use the same backend.
  • Innovation: Third‑party developers can build new tools on top of existing services.
  • Security: You can expose only what’s needed, keeping internal logic hidden.

Not-so-good things

  • Complexity: Designing a clean, versioned API takes careful planning.
  • Dependency: If an external API changes or goes down, your app can break.
  • Performance: Network latency adds delay compared to local function calls.
  • Rate limits: Too many requests can be blocked, requiring extra handling.
  • Security risks: Poorly secured APIs can expose data or be abused by attackers.