Free AI app builder — web & Android

Build full apps with AI.
Pay nothing but the tokens you use.

DemonBuild turns a prompt into a working web app — React, Next.js-style builds included — right in your browser or on your phone. There is no subscription, no account, and no cloud project storage. You bring a prepaid DemonRoute API key; the key is the login; everything you build stays on your device.

Launch DemonBuild ↗ Get an API key ↗

No subscription · No account · No cloud storage · No other keys accepted

Features

A real builder, not a demo toy

Full app generation

Multi-file web apps from a prompt — HTML/CSS/JS and React builds with bundled, version-pinned dependencies via esbuild-wasm and esm.sh.

Agentic build loop

The agent plans, writes files, previews, and fixes its own build errors with feedback from the in-browser bundler.

Live preview

Generated code runs in an isolated sandboxed preview, separate from your key and your projects.

Your choice of 560+ models

Every model on DemonRoute is available — uncensored coders, 1M-context flagships, cheap 7B workhorses. Prices shown live from the gateway.

Honest token meter

Running token and dollar totals as the build works, computed from the gateway's own pricing. No estimates, no surprises.

ZIP export / import

Your projects are yours. Export any project as a portable ZIP, import it anywhere, keep the definitive backup locally.

Undo & session restore

Full snapshot history — roll back any agent edit, and pick up exactly where you left off.

Android app

The same builder on your phone, keys protected by Android Keystore-backed storage. One codebase, no compromise.

Free forever

The builder itself costs nothing and never will. You only pay for the inference your builds actually consume.

Privacy by architecture, not by policy

There is nothing on our servers to leak

Most AI builders store your prompts, your projects, and your identity on their infrastructure. DemonBuild can't — the storage doesn't exist.

Projects never leave your device. Stored in your browser's IndexedDB or the app's local storage. We have no project database.
No accounts. Your DemonRoute API key is the only credential. We don't know your name, email, or what you build.
Your key is never shipped to us. The app calls api.demonroute.com directly. Keys live in memory by default, or Android Keystore on mobile.
No analytics on you. No trackers, no fingerprinting, no session replay. Build counts, never identities.
Prepaid, hard stop at $0. Your balance can never go negative. A build that runs out of credit simply pauses — top up and continue.
Failed calls are never charged. DemonRoute audits every upstream call and refunds failures automatically, every 5 minutes.

How it works

Three steps, two minutes

Get a key

Paste it in

Open DemonBuild on web or Android and paste your key. That's the entire login. Nothing else to configure.

Describe your app

Tell the agent what to build. Watch it plan, write, preview, and iterate — with a live meter of exactly what it costs.

Why free?

The subscription is the scam we're skipping

	DemonBuild	Typical AI builders
Builder app	Free	$20–25 / month
Account required	None	Email + identity
Project storage	Your device only	Their cloud
You pay for	Tokens you actually use	Seats, limits, overages
Failed generations	Refunded automatically	Still billed
Model choice	560+ incl. uncensored	Their pick, their rules

We make money the honest way: when your builds use tokens, you buy them at DemonRoute's listed prices — prepaid, metered, refundable. The app is the free part because it should be.

Build full apps with AI.Pay nothing but the tokens you use.