/canvas

Canvas Skill

Display HTML content on connected OpenClaw nodes (Mac app, iOS, Android).

Overview

The canvas tool lets you present web content on any connected node's canvas view. Great for:

• Displaying games, visualizations, dashboards
• Showing generated HTML content
• Interactive demos

How It Works

Architecture

┌─────────────────┐     ┌──────────────────┐     ┌─────────────┐
│  Canvas Host    │────▶│   Node Bridge    │────▶│  Node App   │
│  (HTTP Server)  │     │  (TCP Server)    │     │ (Mac/iOS/   │
│  Port 18793     │     │  Port 18790      │     │  Android)   │
└─────────────────┘     └──────────────────┘     └─────────────┘

1. **Canvas Host Server**: Serves static HTML/CSS/JS files from `canvasHost.root` directory 2. **Node Bridge**: Communicates canvas URLs to connected nodes 3. **Node Apps**: Render the content in a WebView

Tailscale Integration

The canvas host server binds based on `gateway.bind` setting:

| Bind Mode | Server Binds To | Canvas URL Uses | | ---------- | ------------------- | -------------------------- | | `loopback` | 127.0.0.1 | localhost (local only) | | `lan` | LAN interface | LAN IP address | | `tailnet` | Tailscale interface | Tailscale hostname | | `auto` | Best available | Tailscale > LAN > loopback |

**Key insight:** The `canvasHostHostForBridge` is derived from `bridgeHost`. When bound to Tailscale, nodes receive URLs like:

http://<tailscale-hostname>:18793/__openclaw__/canvas/<file>.html

This is why localhost URLs don't work - the node receives the Tailscale hostname from the bridge!

Actions

| Action | Description | | ---------- | ------------------------------------ | | `present` | Show canvas with optional target URL | | `hide` | Hide the canvas | | `navigate` | Navigate to a new URL | | `eval` | Execute JavaScript in the canvas | | `snapshot` | Capture screenshot of canvas |

Configuration

In the active OpenClaw config file (`$OPENCLAW_CONFIG_PATH`, default `~/.openclaw/openclaw.json`):

{
  "canvasHost": {
    "enabled": true,
    "port": 18793,
    "root": "/Users/you/clawd/canvas",
    "liveReload": true
  },
  "gateway": {
    "bind": "auto"
  }
}

Live Reload

When `liveReload: true` (default), the canvas host:

• Watches the root directory for changes (via chokidar)
• Injects a WebSocket client into HTML files
• Automatically reloads connected canvases when files change

Great for development!

Workflow

1. Create HTML content

Place files in the canvas root directory (default `~/clawd/canvas/`):

cat > ~/clawd/canvas/my-game.html << 'HTML'
<!DOCTYPE html>
<html>
<head><title>My Game</title></head>
<body>
  <h1>Hello Canvas!</h1>
</body>
</html>
HTML

2. Find your canvas host URL

Check how your gateway is bound:

CONFIG_PATH="${OPENCLAW_CONFIG_PATH:-${OPENCLAW_STATE_DIR:-$HOME/.openclaw}/openclaw.json}"
cat "$CONFIG_PATH" | jq '.gateway.bind'

Then construct the URL:

• **loopback**: `http://127.0.0.1:18793/__openclaw__/canvas/<file>.html`
• **lan/tailnet/auto**: `http://<hostname>:18793/__openclaw__/canvas/<file>.html`

Find your Tailscale hostname:

tailscale status --json | jq -r '.Self.DNSName' | sed 's/\.$//'

3. Find connected nodes

openclaw nodes list

Look for Mac/iOS/Android nodes with canvas capability.

4. Present content

canvas action:present node:<node-id> target:<full-url>

**Example:**

canvas action:present node:mac-63599bc4-b54d-4392-9048-b97abd58343a target:http://peters-mac-studio-1.sheep-coho.ts.net:18793/__openclaw__/canvas/snake.html

5. Navigate, snapshot, or hide

canvas action:navigate node:<node-id> url:<new-url>
canvas action:snapshot node:<node-id>
canvas action:hide node:<node-id>

Debugging

White screen / content not loading

**Cause:** URL mismatch between server bind and node expectation.

**Debug steps:**

1. Check server bind: `CONFIG_PATH="${OPENCLAW_CONFIG_PATH:-${OPENCLAW_STATE_DIR:-$HOME/.openclaw}/openclaw.json}"; cat "$CONFIG_PATH" | jq '.gateway.bind'` 2. Check what port canvas is on: `lsof -i :18793` 3. Test URL directly: `curl http://<hostname>:18793/__openclaw__/canvas/<file>.html`

**Solution:** Use the full hostname matching your bind mode, not localhost.

"node required" error

Always specify `node:<node-id>` parameter.

"node not connected" error

Node is offline. Use `openclaw nodes list` to find online nodes.

Content not updating

If live reload isn't working:

1. Check `liveReload: true` in config 2. Ensure file is in the canvas root directory 3. Check for watcher errors in logs

URL Path Structure

The canvas host serves from `/__openclaw__/canvas/` prefix:

http://<host>:18793/__openclaw__/canvas/index.html  → ~/clawd/canvas/index.html
http://<host>:18793/__openclaw__/canvas/games/snake.html → ~/clawd/canvas/games/snake.html

The `/__openclaw__/canvas/` prefix is defined by `CANVAS_HOST_PATH` constant.

Tips

• Keep HTML self-contained (inline CSS/JS) for best results
• Use the default index.html as a test page (has bridge diagnostics)
• The canvas persists until you `hide` it or navigate away
• Live reload makes development fast - just save and it updates!
• A2UI JSON push is WIP - use HTML files for now