'## What I Built
Eight developer tools that run entirely in your browser — no files uploaded, no server-side processing, no tracking.
| Tool | Description |
|---|---|
| JSON Formatter | Beautify, validate, compress JSON. CSV export |
| Image → Base64 | Drag & drop, instant Data URI generation |
| SQL Formatter | Pretty-print with keyword highlighting |
| Markdown → HTML | Real-time GFM preview with code blocks |
| UUID Generator | Crypto-secure UUID v4 + ULID |
| Regex Tester | Real-time match highlighting |
| Timestamp Converter | Unix seconds/ms ↔ date |
| Diff Checker | Line-by-line comparison |
Why
Every other online dev tool uploads your data. These run 100% client-side — nothing leaves your browser.
Tech
Pure HTML/CSS/JS. Zero frameworks. Under 30KB. Loads in 50ms.
Try
👉 https://matengtian.github.io/devtools/
Feedback welcome! What tool should I add next?