The Problem
We've all been there. You're debugging an API response, need to format some JSON, or quickly convert a YAML config file. You open a random online tool, paste your data, and... boom.
You just sent your production API keys, database credentials, or customer PII to an unknown third-party server.
I got tired of that risk. I also got tired of having 15 tabs open just to format JSON, test a regex, compare two files, or generate a hash.
The Solution: DevTolkit
I built DevTolkit — a clean, modern, offline-first Swiss Army knife for developers.
Everything runs 100% in your browser. Zero data ever leaves your machine.
🔧 What's inside?
| Tool | What it does |
|---|---|
| JSON Formatter | Validate, format, and minify JSON with syntax highlighting |
| YAML ↔ JSON | Convert YAML to JSON and vice versa (perfect for K8s configs) |
| CSV Converter | Convert CSV to JSON and JSON to CSV |
| Base64 | Encode and decode Base64 strings |
| URL Encoder | Encode/decode URL parameters |
| Crypto Hashes | Generate MD5, SHA-1, SHA-256, SHA-512 hashes |
| Visual Diff | Compare two texts side-by-side with color-coded differences |
| JSONPath | Query and test JSONPath expressions on your JSON data |
| Regex Tester | Test regular expressions with real-time matches and groups |
| Dark / Light Themes | Multiple themes and accent colors for your eyes |
🚀 Why it's different
- 🔒 Privacy-first – Your data never touches a server. Not even mine.
- 📡 Works offline – It's a Progressive Web App (PWA). Install it and use it anywhere.
- 🎨 Modern UX – No clutter, no ads, no sign-ups. Just open and work.
- 💻 Open Source – All code is on GitHub. Audit it, fork it, contribute.
🛠️ Tech Stack
- Vanilla JavaScript (no frameworks, no bloat)
- CSS3 with CSS variables for theming
- Service Workers for offline support
- Web Workers for heavy processing (so your UI never freezes)
🙋 Who is this for?
- Backend / DevOps engineers – Safe handling of configs and secrets.
- Frontend developers – Quick API debugging and JSON manipulation.
- Students / Juniors – Learn about JSON, YAML, regex, and hashing with a visual tool.
- Freelancers – A reliable toolbox when you're offline at a coffee shop.
🔗 Try it now
👉 Live demo: https://pepe8173bbb.github.io/DevTolkit/
👉 Source code: https://github.com/pepe8173bbb/DevTolkit
🤔 What's next?
I'm actively working on:
- Support for larger files (streaming)
- JWT Debugger
- SQL Formatter
💬 I'd love your feedback
- What feature do you use the most?
- What tool am I missing?
- Does the Diff visualizer feel intuitive?
Drop a comment below or open an issue on GitHub. If you like it, please give it a ⭐ star — it really helps!
Thanks for reading! 🙌
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