---
title: "Run the demo app"
description: "How to clone, install, and run the Wavelength demo app locally against signet, testnet, or a custom backend."
canonical: https://wavelength.lightning.engineering/web/get-started/run-the-demo-app/
---

> Docs index: https://wavelength.lightning.engineering/llms.txt

# Run the demo app

> **Try it live**
>
> A hosted signet demo runs in your browser at <https://wavelength.lightning.engineering/demo/>. No clone or local setup required.

## Clone & install

The reference integration lives in the Wavelength monorepo at `apps/web-wallet-demo`. Clone the repository, install dependencies with pnpm, and build the workspace packages:

```bash
git clone https://github.com/lightninglabs/wavelength-sdk.git
cd wavelength-sdk
pnpm install
pnpm build
```

The demo depends on the workspace packages `@lightninglabs/wavelength-web` and `@lightninglabs/wavelength-react`. The runtime WASM binaries under `apps/web-wallet-demo/public/runtime/` are gitignored and ephemeral, so stage them before running the demo:

```bash
pnpm --filter web-wallet-demo run wasm:local
```

See [Hosting runtime assets](/web/get-started/hosting-runtime-assets/) for details on what this stages and how to point the demo at a different asset source.

## Run

Start the Vite dev server from the monorepo root. Locally built runtime assets cannot match the pinned release digests, so `dev:local` disables integrity verification for this flow (`VITE_RUNTIME_INTEGRITY=off`):

```bash
pnpm --filter web-wallet-demo run dev:local
```

Open the URL Vite prints (typically `http://localhost:5173`). The demo boots a **signet** wallet out of the box: the create-wallet screen preselects signet, using the preset `endpointsForNetwork('signet')` returns in `src/lib/runtime-config.ts`, which mirrors the same public gateway URLs `defaultConfig('signet')` would produce. No local backend is required.

Cross-origin isolation headers are configured in the demo’s Vite config so OPFS persistence works in every supported browser. See [Cross-origin isolation](/web/get-started/cross-origin-isolation/) for why these headers are required and how to configure them outside of Vite:

```ts
const crossOriginIsolation = {
  'Cross-Origin-Opener-Policy': 'same-origin',
  'Cross-Origin-Embedder-Policy': 'require-corp',
  'Cross-Origin-Resource-Policy': 'same-origin',
};

export default defineConfig({
  server: { headers: crossOriginIsolation },
  preview: { headers: crossOriginIsolation },
});
```

Use `pnpm --filter web-wallet-demo run build:local && pnpm --filter web-wallet-demo preview` to serve the production build with the same headers: locally built runtime assets cannot match the pinned release digests, so the plain `build` script would fail the integrity check the same way plain `dev` does.

## Optional (testnet)

**Rebuilding runtime assets.** Re-run `wasm:local` whenever you change the daemon: it runs `make wasm-wallet` in wavelength (expecting a sibling checkout, overridable with `WAVELENGTH_DIR`) and copies the full `RUNTIME_ASSET_FILES` set into `public/runtime/<RUNTIME_MANIFEST_VERSION>/`, the versioned path the demo’s `runtimeBaseUrl` points at.

**Testnet.** Select testnet on the create-wallet screen to boot with the preset `endpointsForNetwork('testnet')` returns, which mirrors the same public gateway URLs `defaultConfig('testnet')` would produce. No local backend is needed.

**Troubleshooting OPFS.** If wallet persistence fails in the browser, confirm COOP/COEP headers are present:

```bash
curl -sI http://localhost:5173 | grep -i cross-origin
```

Both `Cross-Origin-Opener-Policy` and `Cross-Origin-Embedder-Policy` must appear in the response. See [Troubleshooting / FAQ](/web/support/troubleshooting/) for more fixes, and the [web guides](/guides/create-a-wallet/) for end-to-end wallet flows built on top of this demo.