Being a developer today means juggling tons of tools — for debugging, formatting, testing APIs, and more. But not every tool needs to come with a monthly subscription!
Here are 10 amazing, free online tools that can help you code smarter, faster, and cleaner in 2025. (Yes, I actually use them every day.)
💻 1. Format JSON Online
If you’ve ever worked with messy or minified JSON, you’ll love this one.
👉 Format JSON Online
lets you format, validate, beautify, and convert JSON data instantly — right in your browser, no sign-in needed.
It even supports JSON-to-CSV, JSON-to-XML, Excel conversion, and an AI JSON Generator that can create or publish mock APIs from plain English prompts. A must-have for frontend devs and API testers.
⚡ 2. CodePen
The go-to place for experimenting with HTML, CSS, and JavaScript. It’s like a playground where creativity meets code.
🧮 3. Regex101
Testing regular expressions can be painful — until you use this. Instant highlighting, explanations, and debugging for your regex patterns.
📊 4. JSON Formatter Chrome Extension
(Also from FormatJSONOnline!) Quickly format and preview JSON responses directly inside your browser tab without leaving the page.
📦 5. Postman
For testing APIs, managing requests, and debugging endpoints, nothing beats Postman. Free plan is enough for most developers.
🧰 6. StackBlitz
Spin up a live coding environment for React, Next.js, or Node instantly — straight in your browser.
🧾 7. Draw.io (diagrams.net)
Create flowcharts, architecture diagrams, and UML charts for your next project with a drag-and-drop interface.
🧠 8. JSONPlaceholder
Need fake REST APIs for frontend projects? JSONPlaceholder provides ready-made endpoints for free — perfect for demos.
💡 9. DiffChecker
Compare code or text files side-by-side. Ideal for spotting subtle differences in configuration files or JSON responses.
🚀 10. Figma
If you’re also into UI design, this one’s for you. It’s collaborative, lightweight, and now even has built-in dev mode for faster hand-off.
🎯 Wrap-Up
Every developer should have a quick-access toolkit of free utilities that make daily tasks easier.
If you’re debugging JSON, testing APIs, or converting data — FormatJSONOnline.com deserves a top spot in your bookmarks.