Sandboxing Python with MicroPython and WASM

Simon Willison's Weblog· June 6, 2026 View original

▶ The 60-second brief

Summary

This post discusses the technique of executing Python code within a secure sandbox environment by leveraging MicroPython and WebAssembly (WASM). It highlights how this combination can enhance security and portability for Python applications.

The concept of running Python code within a sandboxed environment is explored, specifically by utilizing MicroPython in conjunction with WebAssembly (WASM). This approach offers a method to isolate Python execution, thereby enhancing security and control over the code's interactions with the host system. MicroPython, a compact implementation of Python 3, is well-suited for resource-constrained environments, while WASM provides a secure, portable, and efficient binary instruction format for web browsers and other platforms. Combining these two technologies allows developers to execute Python logic in a highly controlled and isolated manner. This technique is particularly valuable for scenarios where untrusted code needs to be run, or where strict resource management and security boundaries are paramount. It opens up possibilities for safer execution of Python scripts in various applications, from web-based tools to embedded systems.

Why it matters

Securely sandboxing Python code is critical for applications that execute user-provided scripts, plugins, or untrusted third-party logic. This method offers a robust solution for enhancing security, preventing malicious actions, and ensuring stable application performance.

How to implement this in your domain

  1. 1Research MicroPython and WebAssembly to understand their individual capabilities.
  2. 2Experiment with setting up a basic sandboxed environment using these technologies for Python execution.
  3. 3Evaluate this approach for securely running user-generated content or third-party plugins in your applications.
  4. 4Consider the performance implications and resource overhead of this sandboxing method for your specific use cases.

Who benefits

Software DevelopmentCybersecurityWeb DevelopmentCloud ComputingEdTech

Key takeaways

  • MicroPython and WASM can be used to sandbox Python code.
  • This method enhances security by isolating code execution.
  • It's useful for running untrusted code or plugins safely.
  • The approach offers portability and efficiency for Python applications.

Original post by Simon Willison's Weblog

"Running Python code in a sandbox with MicroPython and WASM"

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