1. StackBlitz – Instant Online IDE for Fullstack Apps

💻 https://stackblitz.com

Run Angular, React, Vue, and Node.js apps instantly in your browser — no setup required.

2. Quokka.js – Live Scratchpad for JavaScript

⚡ https://quokkajs.com

See real-time execution results for your JavaScript or TypeScript code directly in your editor.

3. Codewars – Gamified Coding Challenges

🥋 https://www.codewars.com

Sharpen your skills with fun, gamified katas that improve problem-solving in multiple languages.

4. Fly.io – Deploy Apps Globally at the Edge

🌍 https://fly.io

Run full-stack apps and databases close to your users worldwide with a few CLI commands.

5. OverAPI – Developer Cheat Sheet Collection

📑 https://overapi.com

One-stop resource for cheat sheets covering languages, frameworks, and dev tools.

6. UI Gradients – Beautiful Gradient Generator

🎨 https://uigradients.com

Pick, tweak, and copy stunning gradient backgrounds for your front-end projects.

7. SQLBolt – Learn SQL the Interactive Way

🧾 https://sqlbolt.com

Practice SQL queries through hands-on lessons and challenges — perfect for beginners and pros alike.

8. Frontend Mentor – Real Projects to Practice Frontend Skills

🖥️ https://www.frontendmentor.io

Build real-world projects with design mockups, then compare your solution with other developers.

9. Refactoring Guru – Learn Design Patterns with Examples

🧩 https://refactoring.guru

Master design patterns and refactoring principles explained in simple, visual examples.

10. Appwrite – Open Source Backend-as-a-Service

🔧 https://appwrite.io

An open-source Firebase alternative that provides authentication, databases, storage, and cloud functions.