I Spent 2 Months Building a 150+ Tool Website with $0 Server Cost

📚 This is Part 1 (Opening) of the UtlKit Tech Series — Next: [Architecture & Trade-offs →] As a frontend developer, I've used countless online tools. And almost all of them suck: Sign-up required — just to format a JSON string? Ad overload — the actual tool gets squeezed into a corner Privacy concerns — your JSON might contain API keys, and the tool sends it to a server Fragmented — formatters on one site, Base64 on another, hashing on a third So I decided to build one that doesn't: no sign-up, no ads, pure client-side computation, data never leaves the browser. The goal was simple — if I need this tool, someone else does too. The result is utlkit.com : 150+ tools, 8 categories, zero server costs. Requirements Requirement Meaning Pure client-side All logic runs in the browser Zero server cost Static hosting, no Node.js backend 150+ pages One page per tool, SEO-friendly Bilingual (EN/ZH) i18n support Dark/Light mode User preference Mobile responsive Works on all devices Why Not Other Frameworks? Option Pros Cons Verdict Vanilla HTML/JS Simple Managing 150+ pages is painful Too slow VuePress / VitePress Fast Docs-oriented, not for interactive tools Not flexible enough Nuxt SSR Powerful Needs a server Violates zero-cost principle Next.js 15 + output: 'export' SSR SEO + client interactivity + static hosting Has pitfalls (covered later) ✅ Best balance The Key Decision: output: 'export' // next.config.js const nextConfig = { output : ' export ' , // Static export trailingSlash : true , // Required for static files images : { unoptimized : true }, // No image optimization server } This means: ✅ Build output is plain HTML/CSS/JS files ✅ Deployable to any static host (Cloudflare Pages, Vercel, GitHub Pages) ✅ Zero server cost ❌ No API Routes, no Server Components, limited dynamic routing Deployment: Zero Cost on Cloudflare Pages Build output : out/ directory, ~14 MB Hosting : Cloudflare Pages Domain : utlkit.com Monthly cost : $0 Build Pipeline npm run build → next build ( o