API Development
Learn, test, debug, and reference APIs in one place. Explore REST APIs, GraphQL, API testing, JSON, authentication, debugging, security, tools, cheatsheets, and interactive playgrounds.
Everything you need to work with APIs
Whether you are learning REST APIs, debugging a production response, testing an endpoint, working with authentication, or looking for a quick reference, this collection brings the related LearnHubly resources together.
Start with the guides, use the developer tools when you need to test something, and use the cheatsheets for quick reference.
📖Learn API Development
Practical guides for understanding APIs and solving real problems.
REST API Complete Guide
Understand REST architecture, resources, HTTP methods, status codes, requests, and responses.
GraphQL vs REST API
Compare REST and GraphQL architecture, performance, flexibility, security, and real-world use cases.
Debug API Responses
Learn how to inspect status codes, headers, JSON payloads, authentication, and common API failures.
HTTP Status Codes Decision Tree
A senior developer's guide for choosing between 200, 201, 204, 400, 401, 403, 404, 409, 422, and 500.
RFC 9457 Problem Details for APIs
Stop returning {success:false}. Structure production-ready machine-readable API error contracts.
API Rate Limiting & Throttling
Token bucket, sliding window algorithms, and distributed rate limiting patterns for scalable APIs.
🛠️API Development Developer Tools
Stop reading and start testing with privacy-first browser utilities.
REST API Tester
Send HTTP requests, inspect responses, headers, status codes, and API payloads directly in your browser.
JSON Formatter
Format, validate, repair, and inspect JSON responses while debugging API requests and integrations.
JWT Decoder
Decode JWT payloads and inspect claims, expiry, and headers during API authentication troubleshooting.
URL Encoder / Decoder
Encode query parameters, paths, and special characters to prevent broken API requests.
URL Parser & Builder
Deconstruct and inspect query parameters, protocol, port, path, and hash fragments.
User Agent Parser
Analyze HTTP User-Agent request headers to debug client detection and device routing.
🧪Practice with Real APIs (API Playground)
Send live requests, test endpoints, inspect responses, and debug payloads right in your browser.
API Playground
Test real public APIs directly from your browser. Build requests, inspect response payloads, check headers, and experiment with API integrations without installing a desktop client.
Practice with Real APIs
Explore available APIs and experiment with different endpoints, request methods, parameters, authentication, and response formats.
GitHub REST API
Query user repositories, commits, pull requests, and issues with bearer tokens.
JSONPlaceholder
Free mock REST API for testing fake users, posts, comments, and todos.
ReqRes API
Realistic user registration, login, pagination, and delayed response simulation.
DummyJSON API
Rich mock eCommerce data for products, carts, recipes, and auth tokens.
📋Quick Reference
Useful references when you don't want to read a full guide.
HTTP Status Codes & Headers Cheatsheet
Quickly understand 2xx, 3xx, 4xx, and 5xx API responses and standard HTTP headers.
cURL Cheatsheet
Common cURL commands for making, inspecting, and debugging HTTP requests from terminal.
JSON Cheatsheet
Quick reference for JSON syntax, structure, data types, and common API serialization patterns.
OpenAI API Cheatsheet
Essential endpoints, parameters, streaming tokens, and prompt payload structures.
🚀Recommended Learning Path
A simple path from understanding APIs to testing them.
Understand Fundamentals
Learn REST, GraphQL, HTTP methods, status codes, resources, requests, and response envelopes.
Build Requests & Headers
Master URLs, query parameters, headers, bearer authentication, content negotiation, and payloads.
Test & Debug Live
Use the REST API Tester and Playground to inspect real payloads, latencies, and edge cases.
Go Deeper with Security
Explore API security, OAuth2 tokens, rate limiting, caching strategies, and resilient microservices.
💡Frequently Asked Questions
Common questions and answers regarding API Development.
REST is an architectural style based on HTTP methods (GET, POST, PUT, DELETE) and fixed resource endpoints that return standard representations (like JSON). GraphQL is a query language allowing clients to request exactly the fields and nested data they need in a single round-trip, eliminating over-fetching and under-fetching.
🔗Explore Related Topics
Continue learning beyond API Development with related collections.
API Security
Authentication, JWT, OAuth2, authorization, secret protection, and secure API design.
JSON Development
JSON formatting, validation, serialization, schema validation, and API payload handling.
Git & Developer Workflow
Git best practices, branching, commits, rebasing, and repository security.
Build, test, debug, and learn APIs
Explore LearnHubly's developer guides, interactive tools, cheatsheets, and API playgrounds to solve real development problems.
Try API Playground →