I built 31 developer tools in a weekend — here's what I learned

A developer built DevKits, a single site with 31 developer tools that run 100% in the browser with no uploads, accounts, or tracking. The site is built with Next.js 15, TypeScript, and Tailwind CSS, and uses a tool registry pattern to auto-generate sitemaps, metadata, and structured data. The project is deployable to Vercel in about two minutes.

Every time I want to format a JSON blob, decode a JWT, or convert a Unix timestamp, I end up on a different random site — each covered in ads, popups, and "click here to install our extension" banners. Half of them upload my data to their server for no reason. So this weekend I built DevKits — a single site with 31 developer tools that all run 100% in the browser . No uploads, no accounts, no tracking. What's in it Right now, 31 tools across 9 categories: - JSON : formatter, validator, JSONPath tester - Converters : JSON ↔ TypeScript / Go / YAML / CSV / XML - Encoding : Base64, URL, HTML entities, image → data URL - Security : JWT decoder, MD5/SHA-256/SHA-512, password generator - Text : regex tester, diff, case converter, word counter, Lorem Ipsum - Web : color converter, user-agent parser - Time : Unix timestamp, cron expression parser - AI : OpenAI/Claude/Gemini token counter - Formatting : SQL, XML, Markdown → HTML Live at devkits.vip https://devkits.vip . Open source? Not yet, but the whole project is deployable to Vercel in ~2 minutes. Why not just use it-tools.tech or smallpdf or …? Fair question. Existing sites have some or all of these problems: - Bloat. Loading 500KB of JS to format 200 characters of JSON. - Ads. Layout shifts on every visit. - Privacy. Some upload your input to a backend to "process" it — a red flag when your input is a JWT or an API response. - Cluttered UX. "Please sign in to save your favorite tools." No thanks. DevKits does the opposite: - Every First Load JS is under 130KB. Most pages are 105–115KB. Zero ads, zero cookies, zero cross-site tracking. - Everything runs client-side. Even the MD5 implementation, the tokenizer, the cron parser — all pure functions in your browser. Every tool page is a single URL you can bookmark. Tech stack - Next.js 15 with the App Router - TypeScript strict mode - Tailwind CSS with @tailwindcss/typography for the Markdown preview - Vercel for hosting I picked Next.js specifically because: - SSG is a first-class citizen. All 41 pages are pre-rendered at build time. No cold starts. - The metadata API is a joy. Per-page title , description , canonical , OpenGraph, and JSON-LD structured data — all just typed objects. - File-based routing scales beautifully. Adding a new tool is: 1 one entry in tools.ts , 2 one page.tsx , 3 one client component. The sitemap, homepage listing, and "related tools" links update automatically. The tool registry pattern my favorite part The whole site is driven by a single tools.ts config file: From this single array, four things are auto-generated: - sitemap.xml — every tool becomes a URL entry - Homepage listing — grouped by category - Per-page metadata — title / description / canonical / OG / Twitter card - JSON-LD structured data — SoftwareApplication + FAQPage schema for rich Google search results The "related tools" section on each page is also just tools.filter t = t.slug == current.slug .slice 0, 6 . So internal linking is automatic. Adding a new tool takes about 20 minutes. The token counter surprised me The AI Token Counter for GPT-4o / Claude / Gemini was the trickiest. Real tokenization requires shipping ~1MB of tokenizer vocabulary. Way too heavy for a "