StemJSON

Mobile apps that build themselves

StemJSON is a new declarative language that turns descriptions into native apps - written by AI, pushed by your backend, or shaped by your users.

See for yourself →
What it is

The language AI uses to build native apps

StemJSON is a declarative language based on JSON, well-suited for AI to generate comprehensive, performant native app UI and logic - whether building new apps or extending existing ones.

The format is open. Drop it into AI tools, prototyping environments, IDE extensions, or alongside hand-written code to simplify and accelerate native app design, development, and delivery.

  • declarative
  • ai-readable
  • native
  • open

Play with it →

Vasyl Krychun
Creator of StemJSON
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Use cases

Where it fits

New pattern

Stem AI Area

A sandboxed area inside your app where end users describe a feature in their own words - and the runtime renders a fully native module on the spot. Apps that adapt to each user, on demand.

An LLM emits StemJSON from the user's prompt; the runtime validates it, renders it natively, and keeps it inside the sandbox you defined. No new binary, no backend round-trip for the UI.

Shipping now: Pluri is the first app in the App Store to use a Stem AI Area - a whole app that quietly rebuilds itself around each user. See it →

Patent pending.

  1. User prompt
  2. LLM
  3. StemJSON
  4. Native module

Other ways to use it

Server-driven UI

Push complete functional modules from your backend - state, actions, expressions, navigation, validation - straight to the device.

your server → StemJSON → device

Prototyping & design tools

From a prompt or a Figma export to a runnable native prototype. Tools emit StemJSON; the runtime renders it on-device - no glue code in between.

Figma / AI tool → StemJSON → runnable app

Alongside hand-written code

Drop StemJSON modules into a native app for the parts that change often - settings, onboarding, content feeds - and keep the rest hand-written.

StemJSON modules + native code → one app

Next steps

Take the tour

Check the spec

Bring coffee. Settle in.

Read, discover, comment, criticise. Sharp feedback sharpens the spec.

Open the spec →

Try the runtime

Bring a phone. Build, break, repeat.

This one is for playing with the runtime, creating something, breaking something, and probably discovering that StemJSON can do more than it should.

Get started →

Browse real apps

Bring curiosity. Maybe a star or two.

Explore real apps to see what's possible, copy the patterns you like, and bookmark anything that sparks an idea.

iOS ↗ Android ↗

Spotted something off in the spec? Open an issue on GitHub ↗ - feedback is the fastest way to make v1.1 better.