Every developer has those moments – you need to quickly format JSON, decode a Base64 string, or test a regex pattern. You don't want to open a heavy IDE or risk pasting sensitive data into an unknown website[reference:17].
Here are 10 free online developer tools that run entirely in your browser. Your data never touches any server[reference:18].
1. JSON Formatter & Validator
URL: https://www.baike300.com/article/167.html
Paste messy JSON, hit format, and get beautifully indented output with syntax validation. It validates your structure, highlights syntax errors, and lets you toggle between compressed and formatted views[reference:19]. Adjustable indentation (2/4 spaces, tabs, minified) and real‑time error detection – it shows exactly where your JSON broke[reference:20].
2. Base64 Encoder / Decoder
URL: https://devtoolshub-seven.vercel.app/tools/base64
Base64 is everywhere – data URLs, JWT tokens, email attachments, and API authentication headers[reference:21]. This tool handles edge cases that raw btoa() and atob() cannot – like Unicode strings and special characters[reference:22]. Full Unicode support including Chinese characters and emoji[reference:23].
3. Regex Tester with Live Preview
URL: https://devtoolshub-seven.vercel.app/tools/regex-tester
Writing a regex without live feedback is like coding blindfolded[reference:24]. This tool gives real‑time match highlighting as you type, supports all common flags (g, i, m, s, u, y), and displays named capture groups[reference:25][reference:26].
4. UUID Generator (Bulk)
URL: https://devtoolshub-seven.vercel.app/tools/uuid-generator
Need a UUID for a database primary key, API identifier, or session token? Generate 1, 5, 10, 25, 50, or 100 at once. Uses crypto.randomUUID() – cryptographically secure[reference:27][reference:28].
5. Timestamp Converter
URL: https://devtoolshub-seven.vercel.app/tools/timestamp
Convert Unix timestamps to human dates and back. Auto‑detects seconds vs milliseconds[reference:29][reference:30]. The "Now" button gives you the current timestamp instantly[reference:31].
6. Color Converter (HEX, RGB, HSL)
URL: https://devtoolshub-seven.vercel.app/tools/color-converter
Convert between HEX, RGB, and HSL formats. Auto‑detects input format, displays a large color preview swatch, and lets you copy any format with one click[reference:32][reference:33].
7. URL Encoder / Decoder
URL: https://devtoolshub-seven.vercel.app/tools/url-encoder
Properly encode URL parameters with special characters. Two modes: encodeURIComponent for thorough encoding and encodeURI for preserving URL structural characters[reference:34][reference:35].
8. JWT Decoder
URL: https://devtoolshub-seven.vercel.app/tools/jwt-decoder
Inspect JWT tokens without a backend. Automatically splits header, payload, and signature, and shows expiry time with green/red status[reference:36].
9. AI ID Photo Generator
URL: https://devtoolshub-seven.vercel.app/tools/ai-id-photo
Remove backgrounds and generate standard ID photos right in your browser. Completely client‑side – no uploads, no server round‑trip[reference:37].
10. DevToolsHub – Complete Collection
URL: https://devtoolshub-seven.vercel.app
All the tools above are part of a larger collection of privacy‑first developer tools. Every tool runs locally in your browser – your data never leaves your machine[reference:38]. No credit card required, no sign‑up needed.
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