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The playground command starts a local playground to test your parser interactively in a web browser.
Aliases: play, pg, web-ui
For this to work, you must have already built the parser as a Wasm module using tree-sitter build --wasm.

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Features

The playground provides:
  • Live parsing - See the syntax tree update as you type
  • Query testing - Test Tree-sitter queries in real-time
  • Syntax highlighting - View highlighted output
  • Error visualization - Easily spot parse errors

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Options

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flag
Don’t automatically open the playground in the default browser. The server will still start and you can manually open the URL.
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path
The path to the directory containing the grammar and Wasm files.
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path
Export static playground files to the specified directory instead of serving them. This allows you to host the playground as a static site.

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Examples

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Start Playground

This will:
  1. Start a local web server
  2. Open the playground in your default browser
  3. Load your parser from the Wasm file

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Start Without Opening Browser

Then manually navigate to the URL shown (typically http://localhost:3000).

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Export Static Files

This creates static HTML, CSS, and JavaScript files that can be hosted on any web server.

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Playground with Custom Grammar Path

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Workflow

Typical development workflow with the playground:
  1. Make changes to your grammar:
  2. Regenerate and build:
  3. Test in playground:
  4. Iterate until satisfied

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Troubleshooting

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Wasm Module Not Found

If you see “Wasm module not found” errors:

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Playground Not Updating

If changes aren’t reflected:
  1. Rebuild the Wasm module
  2. Hard refresh your browser (Ctrl+Shift+R or Cmd+Shift+R)
  3. Clear browser cache if needed

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Port Already in Use

If the default port is busy, the CLI will try alternative ports automatically.