AI App Maker With No Backend

The strict reading is: the running app has no server-side code that you wrote or that the builder generated for you. No Express, no Next.js API route, no Supabase or Convex calls, no per-user database. State lives in React useState, persistence (if any) lives in localStorage or IndexedDB, and the deployed artifact is a folder of static files served by any CDN. mk0r's pre-baked sandbox holds itself to that standard. The only "infrastructure" file in the scaffold at /app is src/_mk0rBridge.ts, and all 28 lines of it do is forward Vite HMR events to the preview parent window via window.parent.postMessage.

Three reasons that come up over and over in weekend-project threads. First, friction: a frontend-only app has no signup, no auth, no "set your password" email, no rate limit, no migration. Second, cost: a static React bundle is free or near-free to host on Cloudflare Pages, GitHub Pages, Netlify, or an S3 bucket. Third, ownership: you can download the bundle, host it yourself, and your data stays on your own device. Most habit trackers, calculators, BMI tools, study cards, color pickers, and offline-first PWAs were never going to need a multi-user database in the first place.

It eagerly provisions optional services in parallel at session start (Neon Postgres, Resend, PostHog, GitHub) and writes whatever was successfully created to /app/.env. But provisioning is not the same as use. The agent is told in /app/CLAUDE.md to "always check that the env var exists before using it" and to only use these services for behaviors that genuinely need them: cross-device persistence, transactional email, analytics, source control. If you ask for a habit tracker, the generated app reads and writes localStorage and the DATABASE_URL sits unused. Verify it yourself: the running preview makes zero network calls beyond Vite's dev-server HMR socket and any explicit fetch the agent wrote into your code.

Three quick checks. Open the network tab in the preview, refresh, interact with the app, and look for any fetch or XHR to a non-localhost URL: if there are none, you are frontend-only. Run grep -ri "fetch(\|axios\|supabase\|fetch " /app/src and grep for DATABASE_URL or RESEND_API_KEY usage: if nothing appears, no server is being called. Check package.json for server dependencies (express, fastify, next, hono, drizzle, pg, prisma, supabase-js): a clean package.json beyond react, react-dom, vite, tailwindcss is the green light.

Lovable, Base44, Appy Pie, Glide, Zite all market themselves as backend-free for the user, which means "we set up Postgres or Firestore on your behalf and hide it." That is fine when your app needs auth, multi-user data, and role-based permissions. It is overkill, and lock-in, when you are building a Pomodoro timer for yourself. mk0r's behavior is closer to the bottom of that ladder by default: a habit tracker stays a habit tracker, a calculator stays a calculator, and the deployed artifact is a static React bundle you could host on a USB stick.

Just say so. "Make this remember my data across browsers" or "add login" flips the agent into reading /app/.env, finding DATABASE_URL or NEON_HOST, and writing the smallest piece of server-side code that satisfies the request. The Postgres database is already there waiting because mk0r provisioned it eagerly at session start; the agent just stops ignoring it. You can also keep the app frontend-only and replace localStorage with an exported JSON file the user uploads to a cloud drive, which is sometimes the right answer.

When you press Publish, mk0r asks for a domain and ships an email notification to provision the mapping. What gets served is whatever the Vite dev server was rendering: React components, Tailwind CSS, optional fetched data. If your app never wrote a server route, the published version doesn't have one either. There is no auto-spun Lambda, no implicit edge function, no proxy that turns your frontend into a serverless backend behind your back. What you wrote is what runs.