Library / Data & backend / API
No. 047·noun·also called application programming interface, endpoint, REST API

API

A defined way for one piece of software to ask another for data or to do something, like a menu with an order window.

SPECIMEN · DIAGRAM · SEQUENCE
Your app
Their API
1GET price for AAPL2{ price: 182.50 }
Definition

What it is

An API is a set of requests a system accepts and the answers it gives back. Your app's frontend uses one to talk to its backend; your backend uses other companies' APIs to send texts, charge cards, or check the weather.

Think of it as a restaurant menu: you don't walk into the kitchen, you order from a fixed list and get a dish back. Each item on the menu is an endpoint.

When you want your app to connect to another service, the question is usually "does that service have an API, and what can it do?"

Say it like a builder

How to ask for it

Vague

“Make it pull in the stock prices.”

Precise

“Fetch the latest price for each ticker in the watchlist from a market data API every 15 minutes, store it with a timestamp, and show "Last updated 3 min ago" on the dashboard.”

Why it works

"Pull in" leaves the source and timing open; naming an API with a refresh schedule and storage plan defines the integration.

In the wild

You've seen this in

  • AA travel site pulling flight prices from airlines
  • YYour app sending texts through Twilio
  • SGoogle Maps embedded in a store locator
Usage note

Often confused with

IntegrationAn integration is the finished connection between two apps; an API is the doorway it goes through.WebhookWith an API you ask for data; with a webhook the other service tells you when something happens.