API basics for beginners

A web API is an address that answers with data instead of a page.

A page for programs

A normal web address gives you a page for people. A web API address gives a program the same kind of answer in a plain format, nearly always JSON. You ask with a request (usually GET, which only reads), and the server answers with a status code and a body.

Example

Ask Open-Meteo for the weather at a latitude and longitude, with the current parameter naming what you need:

curl -L "https://api.open-meteo.com/v1/forecast?latitude=30.9&longitude=75.85&current=temperature_2m,wind_speed_10m"

The answer is a JSON text with names and values, such as the temperature and its unit. On every API page of this directory you will find that request in curl, Python and JavaScript, a box to try it, and a real answer.

The parts of a request

1. The address, such as https://api.example.com/v1/items.
2. Parameters, after a question mark and joined by &: ?latitude=30.9&longitude=75.85.
3. The method: GET to read. POST, PUT and DELETE change data and usually need a key.
4. Headers: extra information, such as the format you accept or a key.

The answer

Look at the status code first: 200 means success, 404 not found, 429 too many requests (see the HTTP codes section of this site). Then read the body: JSON has curly brackets for objects and square brackets for lists.

Keys

Many APIs need a key that identifies you. Keys must never be put into a web page, because anyone can read the page. The APIs in this directory need no key, so they are safe for first steps.

This is an independent directory. It is not connected with any of the services listed. Each address was called on 14 November 2026 with curl, Python, Node.js and Chrome (from a page on another site), and the answer shown is a real one. APIs change: check the service's own page before you depend on it.