Learn how applications communicate across the internet
Web APIs (Application Programming Interfaces) are the bridges that allow different software applications to communicate with each other over the internet. They define the rules, protocols, and tools for how applications can request and exchange data.
Learning Objectives
You'll understand REST principles, API authentication, rate limiting, and how to work with real APIs through hands-on demonstrations using a weather API example.
Real-world analogy:
Think of APIs like a restaurant menu and waiter. The menu (API documentation) tells you what you can order and how. You make requests to the waiter (API endpoint) who brings back your food (data) from the kitchen (server).
1REST API Fundamentals
REST (Representational State Transfer) is the most common architectural style for web APIs. It uses standard HTTP methods and follows predictable URL patterns to perform operations on resources. We'll use a fictional weather API (api.example-weather.com) as our example throughout this lesson.
Most APIs require authentication to control access, track usage, and protect resources. API keys and tokens are the most common methods for identifying and authorizing requests.
How API Keys Work
API keys are unique identifiers that authenticate your requests. Think of them like a membership card that proves you're allowed to use the service.
Example API Request with Key:
GET /api/weather/current/london HTTP/1.1
Host: api.example-weather.com X-API-Key: wth_9a8b7c6d5e4f3g2h1i0j9k8l7m6n5o4p
Security Tip: Never share your API keys publicly or commit them to GitHub. Treat them like passwords!
Click button to generate a practice API key
What happens without a valid key?
Response:
3Rate Limiting & Usage Control
APIs implement rate limiting to prevent abuse, ensure fair usage, and maintain service quality. Rate limits control how many requests you can make within a specific time window.
Rate Limit Information
Requests Used:
150 / 500 per hour
Common Rate Limit Headers:
X-RateLimit-Limit: 500
X-RateLimit-Remaining: 350
X-RateLimit-Reset: 1642680000 // Reset time as Unix timestamp
Rate Limit Exceeded - HTTP 429
{
"error": "Rate limit exceeded",
"message": "Too many requests. Limit: 500 per hour",
"retry_after": 3600
}
4Complete API Simulation
Let's put it all together with a simulated weather API that demonstrates REST endpoints, authentication, rate limiting, and error handling. This is a safe practice environment - no real API calls are made.
📝 Note: Simulated Environment
This is a simulation showing how real APIs work. No actual API calls are made - all responses are generated locally for learning purposes.