I Built 22 Free Developer Tools in a Weekend — Here's What I Learned

Neo Ahn — Sat, 28 Mar 2026 08:15:10 +0000

The Idea

I kept bookmarking random utility sites — one for JSON diff, another for regex testing, another for Base64 encoding. Each
had different UIs, aggressive ads, and some even sent my data to their servers.

So I built mydevtools.dev — 22 developer tools in one place, with a consistent VS Code-style
dark theme, and everything processing 100% in the browser.

## What's Inside

### Data & Text

JSON Diff — Side-by-side comparison using Monaco Editor
JSON Formatter — Beautify, minify, validate
Text Diff — Line-by-line text comparison
CSV to JSON — Bidirectional conversion
JSON to YAML — Bidirectional conversion
Word Counter — Words, characters, sentences, reading time

### Encoding & Conversion

Base64 Encoder/Decoder — Full UTF-8 support
URL Encoder/Decoder — With query string parser
HTML Entity Encoder — Escape/unescape HTML
Number Base Converter — Binary, octal, decimal, hex

### Security & Identity

JWT Decoder — Header, payload, expiration check
Hash Generator — MD5, SHA-1, SHA-256, SHA-384, SHA-512
UUID Generator — Bulk generate with format options
Password Generator — Customizable strength, bulk mode

### Developer Utilities

Regex Tester — Real-time matching, 18 pattern presets, URL sharing
Cron Expression Parser — Human-readable explanations, next run times
Timestamp Converter — Unix ↔ date, live current time
Markdown Preview — Live editor with rendered output

### Visual & Media

Color Converter — HEX ↔ RGB ↔ HSL with live preview
QR Code Generator — Customizable size, download as PNG
Image to Base64 — Drag & drop, multiple output formats
Lorem Ipsum Generator — Words, sentences, paragraphs

## Tech Stack

Next.js 16 (App Router, SSG for SEO)
Tailwind CSS 4 (VS Code-inspired dark theme)
TypeScript (strict mode)
Vercel (free tier hosting)
No backend — everything runs client-side

Total hosting cost: $0/month (excluding domain).

## Key Decisions

Why no external libraries for most tools?
Base64 uses btoa/atob, hashing uses Web Crypto API, UUID uses crypto.randomUUID(). The only external packages are
Monaco Editor (for JSON Diff), qrcode (for QR generation), and jsondiffpatch (for structural JSON comparison). Keeping
dependencies minimal means faster load times and fewer security concerns.

Why VS Code theme?
Developers already spend 8+ hours a day in VS Code. A familiar dark theme means zero cognitive load switching between tools.

Why 100% client-side?
Privacy is a feature. When you paste a JWT token or API response into a tool, you don't want it hitting someone else's
server. Every tool on the site processes data entirely in your browser.

## SEO Strategy

Each tool has its own page with unique metadata. The regex tester has 15 pattern-specific landing pages
(/regex/patterns/email, /regex/patterns/url, etc.) targeting long-tail keywords. Total: 39 indexed pages from a single
project.

## What's Next

Adsense integration (once approved)
More tools based on user feedback
Additional SEO content pages

## Try It

mydevtools.dev

What tools do you wish existed? Drop a comment — I might build it next.

DEV Community: Neo Ahn

I Built 22 Free Developer Tools in a Weekend — Here's What I Learned

The Idea