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Master the Language of Modern Software

The most comprehensive, reliable, and friendly guide for API beginners. From HTTP basics to advanced architectures, we cover it all.

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100+ Articles
50+ Interactive Examples
Free Open Source 
GET /api/v1/knowledge HTTP/1.1
Host: learnapi.org
Accept: application/json

# Response
HTTP/1.1 200 OK
Content-Type: application/json

{
  "mission": "Empower developers",
  "topics": [
    "REST", 
    "GraphQL", 
    "gRPC",
    "WebSocket"
  ]
}

Core Curriculum

Structured to help you both consume and build world-class APIs.

Mastering Existing APIs

🚀
01

Get Started

First steps in the world of APIs. Setup and Quickstart.
🌱
02

API Fundamentals

Understanding HTTP, JSON, and the basic building blocks.
🧰
03

Working with APIs

Authentication, environments, and team collaboration.
👻
04

Mocking APIs

Simulate responses to frontend before the backend is ready.

Building Your Own APIs

🎨
05

Designing APIs

REST constraints, resource modeling, and OpenAPI specs.
🛠
06

Developing APIs

Implementation strategies, frameworks, and best practices.
🧪
07

Testing APIs

Automated testing, assertions, and quality assurance.
📝
08

API Documentation

Creating clear, interactive docs for your stakeholders.

Supported Protocols

Deep dives into modern communication standards.

HTTP/REST

The standard for web APIs.

 GraphQL

Flexible data queries.

 SOAP

Enterprise legacy standards.

 WebSocket

Real-time bidirectional.

 gRPC

High performance RPC.

 SSE

Server-Sent Events.

API Lifecycle Management

Master the journey from concept to retirement.

🔄

Lifecycle Stages

Plan, Design, Develop, Test, Deploy, Retire.
⚖️

API Governance

Ensuring consistency and compliance.
🛡️

API Security

Best practices to protect your endpoints.
📈

API Monitoring

Track performance and usage in production.

Common Questions

Quick answers to untangle API concepts.

What is an API?

API stands for Application Programming Interface. It's a set of rules that allows different software applications to communicate with each other.

Read Guide →

How do I read API Docs?

Good documentation explains endpoints, parameters, and authentication. Look for the "curl" examples and response schemas to understand how to interact.

Learn More →

What is SSE?

SSE (Server-Sent Events) allows a server to push real-time updates to a client over a single HTTP connection. It's great for news feeds and tickers.

Explore SSE →

What is OpenAPI Spec?

OpenAPI (formerly Swagger) is a standard for defining REST APIs. It describes endpoints, request/response formats, and auth methods in a machine-readable JSON or YAML file.

View Specification →

How do I call an API?

You can make requests using command-line tools like cURL, UI clients like Apidog or Postman, or code libraries like Axios (JS) and Requests (Python).

See Examples →

How to use AI with APIs?

AI tools can generate OpenAPI specs from natural language, create automated test scenarios, write documentation, and even build mock servers instantly.

AI Workflows →
Live Demo

Experience a Real API

Don't just read about APIs—interact with one. The PetStore API is a comprehensive example demonstrating CRUD operations, authentication, and error handling.

Try PetStore API ↗ 
POST /pet HTTP/1.1
Content-Type: application/json

{
  "name": "doggie",
  "photoUrls": [
    "https://example.com/image.jpg"
  ],
  "status": "available"
}

Explore Popular APIs

Discover thousands of public APIs on the API Hub. Here are some favorites to get you started.

🤖

OpenAI API

Power your apps with ChatGPT and DALL·E models.
💳

Stripe API

The standard for online payments and subscriptions.
🐦

Twitter/X API

Access tweets, users, and trends data programmatically.
🎮

Discord API

Build bots and integrate with gaming communities.
💬

Slack API

Automate workflows and build bots for collaboration.
📝

Notion API

Connect your tools to pages, databases, and notes.
🐙

GitHub API

Manage repositories, issues, and code workflows.
📺

YouTube API

Upload videos, manage playlists, and get analytics.
Browse API Hub ↗