Every developer has that moment: you need to decode a JWT, format some JSON, or convert a timestamp — and you end up on a sketchy site plastered with ads that may or may not be uploading your data to a server in who-knows-where.
I got tired of it, so I built DevToolBox — a collection of 50 free, browser-based developer tools. No signup, no server calls, no tracking. Everything runs in your browser using plain JavaScript.
What's Inside
Here's a quick overview of the tool categories:
Formatters & Validators
- JSON Formatter & Validator — Pretty-print, minify, and validate JSON with syntax highlighting
- HTML Formatter — Beautify messy HTML
- SQL Formatter — Format SQL queries with keyword uppercasing
- XML Formatter — Indent and validate XML
- CSS & JavaScript Minifiers
Encoders & Decoders
- Base64 Encode/Decode — Text and file encoding
- URL Encode/Decode — Handle special characters in URLs
- JWT Decoder — Inspect JWT headers, payloads, and expiry
- HTML Entity Encoder — Named, numeric, and hex entities
- Image to Base64, Text to Binary, and more
Generators
- UUID Generator — v4 UUIDs with bulk generation
- Password Generator — Cryptographically secure passwords with strength indicator
- Lorem Ipsum Generator — Placeholder text by words, sentences, or paragraphs
- QR Code Generator — Pure JS QR encoder with SVG/PNG download
- Placeholder Image Generator, Favicon Generator, and more
Converters
- Timestamp Converter — Unix epoch to human-readable and back
- YAML to JSON — Bidirectional conversion
- JSON to CSV — RFC 4180 compliant
- JSON to TypeScript — Generate TS interfaces from JSON
- Color Converter, CSS Units Converter, Number Base Converter, Data Size Converter, Time Zone Converter
CSS Visual Tools
- Box Shadow Generator — Visual editor with multi-layer support
- Gradient Generator — Linear and radial gradients with color stops
- CSS Units Converter
Text & Code Tools
- Regex Tester — Real-time matching with flag support
- Diff Checker — Side-by-side text comparison using LCS algorithm
- Markdown Preview — Live preview with pure JS parser
- Word Counter, String Case Converter, Line Sorter, and more
Reference Tools
- HTTP Status Codes — Searchable reference for all 44 status codes
- Cron Expression Parser — Parse cron + show next execution times
- Chmod Calculator — Interactive permission grid with presets
- ASCII Table — Searchable reference (0-255)
Why Browser-Based Matters
Every tool on DevToolBox processes data entirely in your browser. Here's why that matters:
- Privacy — Your API keys, JWTs, passwords, and config files never leave your machine. There's no server to get breached.
- Speed — No network round-trip. Paste your data, get results instantly.
- Offline capable — After the initial page load, most tools work without an internet connection.
- No rate limits — Format a million JSON objects if you want. It's your CPU.
Tech Stack
For the curious:
- Next.js with static site generation (59 pages pre-rendered at build time)
- Tailwind CSS + shadcn/ui for the UI
- Dark mode with system preference detection
- Zero external API dependencies — every tool is pure JavaScript
- Deployed on Vercel (free tier handles it easily)
What's Next
I'm planning to keep adding tools based on what developers actually need. If you have suggestions for tools you'd like to see, drop a comment below.
Check it out: toolbox-dev.com
All tools are free forever. No signup required. No data collection. Just open and use.
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