Originally published on DevToolsHub — a collection of free, privacy-first online tools for developers.
Every developer has those moments — you need to quickly format some JSON, decode a Base64 string, or test a regex pattern, but you don't want to open a heavy IDE or risk pasting sensitive data into an unknown website.
I've been maintaining a collection of privacy-first developer tools that run entirely in your browser. Your data never touches any server. Here are 10 tools that I use almost daily.
1. 🔧 JSON Formatter & Validator
The most requested tool in any developer's arsenal. Paste messy JSON, hit format, and get beautifully indented output with syntax validation.
Why use it:
- Format with adjustable indentation (2/4 spaces, tabs, minified)
- Real-time error detection — highlights exactly where your JSON broke
- Copy formatted output with one click
👉 Try it: DevToolsHub JSON Formatter
2. 🔄 Base64 Encoder / Decoder
Need to quickly encode an API token or decode a JWT header? Base64 encoding is everywhere in web development.
Why use it:
- Full Unicode support (Chinese characters, emoji, etc.)
- Automatic detection — paste Base64 and it auto-decodes
- Toggle between encode/decode with one click
3. 🎯 Regex Tester with Live Preview
Regex is powerful but notoriously hard to debug. This tool gives you real-time matching feedback so you can see exactly what your pattern captures.
Why use it:
- Live matching as you type (300ms debounce)
- Supports all flags: g, i, m, s, u, y
- Named capture groups
(?<name>...)support - Highlighted matches in the test string
👉 Try it: DevToolsHub Regex Tester
4. 🔑 UUID Generator
Need a UUID for a database primary key, API identifier, or session token? Generate them in batches.
Why use it:
- Generate 1, 5, 10, 25, 50, or 100 UUIDs at once
- Uses
crypto.randomUUID()— cryptographically secure - One-click copy all
👉 Try it: DevToolsHub UUID Generator
5. ⏱ Timestamp Converter
Unix timestamps are everywhere in APIs and databases. This bidirectional converter saves you from mental math.
Why use it:
- Convert timestamp → human date, and date → timestamp
- Auto-detects seconds vs milliseconds
- "Now" button for current timestamp
👉 Try it: DevToolsHub Timestamp Converter
6. 🎨 Color Converter
Designers and frontend developers: need to convert between HEX, RGB, and HSL? This tool has you covered.
Why use it:
- Auto-detects input format
- Large color preview swatch
- Copy any format with one click
👉 Try it: DevToolsHub Color Converter
7. 🔗 URL Encoder / Decoder
URL parameters with special characters breaking your API calls? Encode them properly.
Why use it:
- Dual mode:
encodeURI(preserves URL structure) orencodeURIComponent(encodes everything) - Swap button to quickly switch encode/decode
- Clean output
👉 Try it: DevToolsHub URL Encoder/Decoder
8. 🔐 JWT Decoder
Inspect JWT tokens without a backend. Decode the header and payload to debug authentication flows.
Why use it:
- Automatically splits header, payload, and signature
- Shows expiry time with green/red status
- Sample JWT pre-filled for testing
👉 Try it: DevToolsHub JWT Decoder
9. 📸 AI ID Photo Generator
Need a passport-style photo for your developer profile? This tool removes backgrounds and generates standard ID photos right in your browser.
Why use it:
- Completely client-side — no uploads
- Multiple standard photo sizes
- Background removal with AI
👉 Try it: DevToolsHub AI ID Photo
10. 📋 UUID v4 vs v7 Comparison
Not a tool, but an essential read if you're deciding which UUID version to use in your next project.
👉 Read: UUID v4 vs v7: Which One to Use
Why These Tools Are Different
Most online developer tools upload your data to a server for processing. DevToolsHub does not.
- ✅ 100% client-side — all processing happens in your browser
- ✅ No data leaves your machine — perfect for sensitive data
- ✅ No account required — just open and use
- ✅ Free forever — no hidden limits or paywalls
What's Next?
I'm actively adding new tools. If there's something you'd like to see, let me know in the comments!
If you found this useful, consider bookmarking DevToolsHub or sharing it with a fellow developer.
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