Developers

Building the next generation of hybrid apps.

1. What is a Relay App?

A Relay App (Clip) is a lightweight application built with the @notapublicfigureanymore/relay-sdk. It runs inside the Relay Shell on a mobile device but has direct access to the host machine via the Helper.

The .rly Bundle Format

Apps are distributed as .rly files, which are secure, encrypted packages containing:

  • Manifest: App metadata, permissions, and identity.
  • Assets: Optimized application code and resources.
  • Signature: Cryptographic signature for verification.

2. Relay vs Native/Expo

While both use React, Relay Clips are fundamentally different from standalone Native or Expo apps.

Traditional (Expo/RN)

  • ✕Isolated: Cannot access the user's computer or local network servers easily.
  • ✕Heavy: Large bundle sizes (20MB+) requiring app store downloads.
  • ✕Slow Updates: Weeks to approve changes through App Store Review.

Relay Clips

  • ✓Connected: First-class access to the host computer's shell, file system, and network.
  • ✓Instant: Tiny bundles (~50KB) that load immediately without installation.
  • ✓Live: Push updates instantly. No review process.

3. The SDK

The @notapublicfigureanymore/relay-sdk provides the hooks and components needed to build native-feeling apps.

usePlatform()

Detects device capabilities and OS information.

const { os, isMobile } = usePlatform();

SafeAreaProvider

Automatically handles notch and safe area insets, syncing with the native shell.

<SafeAreaProvider>
  <YourApp />
</SafeAreaProvider>

4. Development Workflow

The Relay CLI makes it easy to scaffold, build, and publish apps.

1. Create App
relay create-app my-new-app
2. Develop
npm run dev

Runs a local development server.

3. Build
relay build

Bundles your app into a single .rly file ready for distribution.