DonDevTool

A local developer multitool — one page, 16 utilities, in a retro terminal / CRT UI. Built with Next.js 16 + TypeScript (strict) and no runtime npm dependencies: every tool runs client-side using native Web APIs (crypto.subtle, crypto.randomUUID, TextEncoder, …) plus small hand-rolled helpers. Nothing you paste ever leaves your machine.

Look & feel

• Retro terminal aesthetic: monospace type, terminal windows, scanlines, a blinking cursor, ASCII flourishes, and a mascot ("Don") throughout.
• Two themes (dark phosphor + light "paper terminal" cream) with a toggle, and a switchable green / amber phosphor accent.
• ⌘K to search tools; tool selection lives in the URL hash.

Fonts (JetBrains Mono + IBM Plex Mono) are self-hosted from public/fonts/, so the app makes zero network requests — truly offline. Regenerate them with node scripts/fetch-fonts.mjs.

Tools

Formatter & converter

• JSON Formatter — format / validate / minify
• JSON ↔ YAML — block-style conversion both ways
• Base64 — encode / decode (UTF-8 safe)
• URL Encode — encode / decode URI components
• Case Converter — camel / Pascal / snake / CONSTANT / kebab / Title / …

Generator

• UUID — v4, in batches
• Hash — MD5, SHA-1, SHA-256, SHA-512
• Password — cryptographically random, configurable character sets
• Lorem Ipsum — paragraphs / sentences / words

Decoder & inspector

• JWT Decoder — header & payload + exp/iat notes (no signature verification)
• Timestamp — Unix epoch ↔ human date (auto s/ms detection, relative time)
• Number Base — binary / octal / decimal / hex (BigInt-backed)
• Color Converter — HEX ↔ RGB ↔ HSL with a live swatch + picker

Tester

• Regex Tester — live matching, highlighting, capture groups, flag toggles
• Cron Parser — validate + preview the next run times
• Text Diff — line-by-line comparison with add/remove stats

Run

npm install
npm run dev

Open http://localhost:3000. Pick a tool from the sidebar (or search); the selected tool is reflected in the URL hash so refreshes and bookmarks stick.

Production build

npm run build
npm start

Architecture

src/
  lib/                      # pure, dependency-free logic (unit-testable)
    cases.ts                # case conversions
    colors.ts               # HEX/RGB/HSL parsing & conversion
    cron.ts                 # 5-field cron parser + next-run calc
    diff.ts                 # LCS line diff
    md5.ts                  # MD5 (not in Web Crypto)
    yaml.ts                 # JSON <-> YAML (block style)
  components/
    ui.tsx                  # shared primitives (Field, Output, CopyButton, …)
    registry.ts             # tool catalog (id, name, category, component)
    AppShell.tsx            # sidebar + search + content, hash routing
    tools/                  # one component per tool
  app/
    page.tsx                # renders <AppShell/>
    layout.tsx

Route handlers / a backend are intentionally absent — every tool is pure client-side computation.

Non-goals

No accounts, no database, no telemetry, no deployment target. It's a personal, offline utility belt.