What is API?

Think of an API like a waiter in a restaurant.

You (the customer) don't go into the kitchen to cook your food. Instead, you tell the waiter what you want, and the waiter communicates with the kitchen. The kitchen prepares your food and the waiter brings it back to you.

The waiter is the API. It's the middleman that takes your request, communicates it to the system that can fulfill it, and delivers the response.

Real examples:

• When you check the weather on your phone, the app uses an API to fetch data from a weather service
• When you pay with Vipps, the store's system uses Vipps's API to process the payment
• When you log in with Google on a website, that site uses Google's API to verify your identity

How APIs Work

An API defines a set of rules for how programs can request and exchange information. Here's the typical flow:

1. Request - Your program sends a request to the API (e.g., "Give me the current weather in Oslo")
2. Processing - The API receives the request and gets the data from its system
3. Response - The API sends back the data in a structured format (usually JSON)

Types of APIs

REST APIs - The most common type. Uses standard web protocols (HTTP). Simple and widely supported.

GraphQL - A newer approach where you specify exactly what data you want. More flexible but more complex.

Webhooks - Instead of you asking for data, the API automatically sends you data when something happens.

What Makes a Good API

• Clear documentation - Explains how to use it
• Consistent design - Predictable patterns
• Proper error messages - Tells you what went wrong
• Rate limiting - Prevents overuse
• Authentication - Ensures only authorized access