How to Execute Untrusted Code Safely with a Sandbox API (Python, JS, Bash)

If you're building an AI agent, coding assistant, or educational platform, you'll eventually need to execute user-submitted code . And if you've ever tried to run eval() on untrusted input, you know that's a one-way ticket to getting pwned. The safe way? Run code in an isolated sandbox — no filesystem access, no network, strict timeouts, resource limits. But setting up Docker containers, gVisor, or Firecracker VMs is a pain. In this post, I'll show you how to execute Python, JavaScript, TypeScript, and Bash code safely using a free sandbox API — zero infrastructure, one HTTP call. Why You Need a Code Sandbox Common use cases: AI agents that write and test code (LLM tool use) Online code editors and playgrounds Coding challenges and interview platforms Education platforms where students run exercises CI/CD pipelines that need quick code validation The risk of running code directly: # Never do this exec ( user_input ) # RCE in 3 characters // Also never do this eval ( userCode ); // Full