Every developer has a collection of bookmarklets and random websites they use for quick utilities: format some JSON, diff two configs, generate a UUID, encode something in base64.
Most of these tools send your data to a server. I built 10 developer utility tools that never leave your browser.
The Stack (or Lack Thereof)
Each tool is one HTML file. No React, no Vue, no build step. Vanilla JS + browser APIs:
- crypto.getRandomValues() for UUIDs, random numbers, secure passwords
- Canvas API for QR code rendering
- localStorage for saving preferences (with try-catch guards)
- LCS algorithm for text diffing
- GitHub-Flavored Markdown parser (regex-based, not a library)
Hosting: GitHub Pages (free, global CDN). No server-side code. No database.
The 10 Tools
1. JSON Formatter & CSV Converter
Format, validate, minify JSON. Convert between JSON and CSV with smart type inference. Handles nested objects and big integers.
2. Text Diff Checker
Compare two texts side by side. Line-by-line and character-level diff using Longest Common Subsequence algorithm. Highlights insertions and deletions.
3. Base64 Encoder & Decoder
Encode/decode text and files to/from Base64. Also includes hex and binary modes. File drag-and-drop support.
4. UUID Generator
Generate UUID v4 (random) and v7 (time-ordered). Batch up to 100 at once. Uses crypto.getRandomValues() for true randomness.
5. Password Generator
crypto.getRandomValues() for secure randomness. Configurable length (8-128 chars), character sets, ambiguous character exclusion. Full entropy — no Math.random() shortcuts.
6. QR Code Generator
Generate QR codes for URLs, WiFi networks, email, SMS, and vCard contacts. Wraps qrcodejs library. Download as PNG.
7. Markdown Editor
Split-pane editor with live preview. GitHub-Flavored Markdown (tables, strikethrough, code blocks). Copy HTML or download.
8. URL Encoder & Decoder
Full URL and component encoding. Data URL generation. Handles edge cases like nested encoding and special characters.
9. Timestamp Converter
Human-readable dates to Unix timestamps (seconds and milliseconds) and vice versa. Timezone-aware ISO 8601 support. Relative time display.
10. Number Base Converter
Binary, octal, decimal, hexadecimal. Fractional number support. Step-by-step conversion mode for learning.
Bonus: Quick Reference Tools
- Case Converter — UPPER, lower, Title, Sentence, camelCase, snake_case, kebab-case
- Word Counter — Words, characters, sentences, paragraphs, reading time
- Random Generator — Numbers, coin flips, dice rolls, list picker, shuffle (crypto.getRandomValues)
- HTML Formatter & CSS Minifier — Tag-aware HTML indentation, CSS whitespace stripping
- Color Picker — HEX/RGB/HSL converter with EyeDropper API support
Why Browser-Native?
Security. Your JSON payloads, API keys, and configuration files never leave your device.
Offline. All tools work without internet after first load. Service workers cache everything.
Speed. No network round-trip. Type a UUID, get it instantly. Diff two files, see results immediately.
Auditable. View source to confirm: no telemetry, no analytics, no hidden API calls.
Free vs PRO
Every tool works fully for free with reasonable limits. The PRO Bundle ($19.99 one-time) removes all limits across all tools with a single license key.
Part of 24 free browser tools — all client-side, no signup, no tracking.
Previously: 7 PDF Tools | 5 Image Tools
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