What is a Web API?

A Web API (Application Programming Interface) is a set of HTTP-based endpoints that allow systems, applications, or devices to communicate over the web.

Examples

Key features

WebapiImage

Types of Web APIs

TypeDescriptionExample
REST APIResource-based, uses HTTP verbs (GET, POST, PUT, DELETE)Twitter API, Shopify API
SOAP APIXML-based, strict contract using WSDLLegacy banking systems
GraphQL APIFlexible querying, client decides what data to fetchGitHub GraphQL API
gRPC APIHigh-performance, uses Protocol Buffers, ideal for microservicesKubernetes API server
WebhooksEvent-driven callbacks sent to a URLStripe sends payment success event

Core Concepts of RESTful Web API

Web API Architecture

A typical Web API architecture includes:

  1. Client (browser, mobile app, other service)

  2. API Gateway / Reverse Proxy (optional, for routing & security)

  3. Web API Layer (controllers, endpoints)

  4. Business Logic Layer (services)

  5. Data Access Layer (database / external APIs)

  6. Persistence (SQL, NoSQL)

  7. Authentication & Authorization (JWT, OAuth2)

Building a Web API (Step-by-Step)

Example: .NET Web API

  1. Create a Project

    dotnet new webapi -n ProductApi

  2. Define Model

    public class Product {
    public int Id { get; set; }
    public string Name { get; set; }
    public decimal Price { get; set; }
}

  3. Create Controller

    [ApiController]
[Route("api/[controller]")]
public class ProductsController : ControllerBase {
    private static List<Product> _products = new();
    
    [HttpGet]
    public IActionResult GetAll() => Ok(_products);

    [HttpPost]
    public IActionResult Create(Product product) {
        product.Id = _products.Count + 1;
        _products.Add(product);
        return CreatedAtAction(nameof(GetAll), product);
    }
}

  4. Run & Test

    • Use Swagger (built into .NET Web API template)

    • Test with Postman or curl

Best Practices for Web APIs

✅ Use Versioning – api/v1/products
✅ Return Proper HTTP Codes – 404 for not found, 400 for bad input
✅ Validation & Error Handling – Always return meaningful errors
✅ Pagination, Filtering, Sorting – For large datasets
✅ Rate Limiting & Throttling – Prevent abuse
✅ Caching – ETag, HTTP cache headers for performance
✅ OpenAPI/Swagger Docs – Self-documenting APIs

Security Considerations

Testing & Monitoring

API Analytics

Track key metrics:

Real-World Use Cases