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Online Playground

The MOL Playground is a browser-based code editor where you can write and run MOL programs instantly — no installation required.

Launch Playground →

Features

  • Instant execution — Write MOL code and run it in your browser
  • Syntax highlighting — Full MOL syntax support
  • Auto-tracing — Pipeline traces appear in the output
  • Share code — Share your programs with others
  • Mobile-friendly — Works on tablets and phones

Security

The playground runs in sandbox mode with these protections:

  • No file system access — read_file, write_file, delete_file are blocked
  • No network access — fetch, serve are blocked
  • Execution timeout — Programs are killed after 10 seconds
  • Code size limit — Maximum 50KB per program
  • Rate limiting — Prevents abuse

Blocked Functions

The following 26 functions are disabled in the playground:

Category Functions
File I/O read_file, write_file, append_file, delete_file, file_exists, file_size, make_dir, list_dir
Path path_join, path_dir, path_base, path_ext
Network fetch, url_encode, serve
System sleep, wait, clock
Security access

All other 117+ stdlib functions work normally.

Self-Hosting

Run your own playground:

# Install with server dependencies
pipx install mol-lang
pip install fastapi uvicorn

# Start the server
cd playground
python server.py

The server starts on http://localhost:8000.

Docker

docker run -p 8000:8000 ghcr.io/crux-ecosystem/mol playground

API

The playground exposes a REST API:

Execute Code

curl -X POST https://mol.cruxlabx.in/api/run \
  -H "Content-Type: application/json" \
  -d '{"code": "show \"Hello from API!\""}'

Response: 

{
  "output": "Hello from API!\n",
  "error": null,
  "execution_time_ms": 12
}

Check Security Info

curl https://mol.cruxlabx.in/api/security

Returns sandbox configuration and blocked function list.