What is an API?

The short answer

An API (Application Programming Interface) is a way for two apps or services to talk to each other and share information.

How does it work?

Think of an API like a waiter at a restaurant. You (the app) tell the waiter (the API) what you want, the waiter takes your order to the kitchen (another app or service), and then brings back what you asked for.

Here’s a real example — when you check the weather on your phone:

  1. The weather app sends a request to a weather service’s API
  2. The API receives the request and fetches the latest forecast data
  3. It sends that data back to your app, which displays it on your screen

Your weather app doesn’t generate forecasts itself. It asks another service for the data through its API.

Where do you encounter APIs every day?

You interact with APIs constantly without realizing it:

  • Logging in with Google or Facebook — the website uses an API to verify your account with Google or Facebook
  • Online payments — when you pay online, the store uses a payment API (like Stripe or PayPal) to process your card
  • Maps in other apps — when a delivery app shows a map, it’s pulling that map from Google Maps or Apple Maps through an API
  • Social media embeds — when a website shows a live Twitter post or YouTube video, it’s using those platforms’ APIs

Why should you care?

Most of the time, you don’t need to think about APIs at all. But knowing what they are helps you understand:

  • Why some apps need an internet connection — they rely on APIs to fetch data from other services
  • Why an app might break but your internet still works — the API it depends on could be down
  • What people mean by “integration” — when two apps “integrate,” they’re usually connected through APIs

When should you worry?

  • “API error” or “connection failed” — this usually means the service the app is trying to reach is temporarily unavailable. Wait a moment and try again.
  • An app stops showing up-to-date info — the API it depends on may have changed or gone offline. Updating the app often fixes this.