just-bash alternatives
The 4 alternatives below are grouped by kind of sandbox, and each says what it does differently from just-bash. Start from whatever made you look: missing GPUs, session limits, self-hosting, pricing or isolation.
Why teams look beyond just-bash
Useful as an agent tool and test double, not as a security boundary for untrusted code.
- Not an OS boundary; runs in your Node.js process without VM isolation
- No real binaries; only the reimplemented command set, Python and JS via WebAssembly
- Beta software; memory containment for WebAssembly needs external process isolation
just-bash alternatives, by kind
Hosted sandbox platforms
SDK-driven sandboxes you create, run code in and destroy through an API.
Vercel Sandbox
Firecracker microVM sandboxes on Vercel’s infrastructure, persistent by default and billed on active CPU, with fine-grained egress control.
- Firecracker microVM
- Pause/resume
How it differs: Teams on Vercel and agent builders who want microVM isolation, active-CPU billing and credential brokering. A polished microVM sandbox with standout egress and billing design; the obvious pick for Vercel-centric teams.
Cloud development environments
Cloud and in-browser development environments that coding agents increasingly run in.
WebContainers
StackBlitz's browser-based Node.js runtime: an operating system in WebAssembly that boots in a browser tab, runs npm/pnpm/yarn and dev servers client-side, and is free for open source with a commercial licence for production use.
- Browser tab (WebAssembly)
How it differs: In-browser coding products and agent UIs that need to run and preview Node.js code on the user's machine with zero server compute. The reference in-browser Node.js runtime for client-side agent code execution, not a substitute for a server-side Linux sandbox.
Isolation primitives and runtimes
The hypervisors, user-space kernels, OS sandboxes and WebAssembly runtimes that sandbox platforms build on.
Pyodide
CPython compiled to WebAssembly, with NumPy, pandas and SciPy ported, running Python inside the browser or Node.js sandbox.
- CPython in Wasm
- Open source
- Self-hostable
How it differs: Running short Python and data-science snippets in a browser tab or Node.js process without a server-side sandbox. The standard way to run Python in a browser or Node sandbox; ideal for short data bursts, unsuitable for anything needing an operating system.
Wasmer
An MIT-licensed WebAssembly runtime and WASIX ecosystem that runs registry packages such as Python, Bash and PHP in local sandboxes, with Wasmer Edge as the hosted option.
- Wasm sandbox
- Open source
- Self-hostable
How it differs: Running interpreter packages (Python, PHP, Bash) in Wasm sandboxes from JavaScript or Python, locally, in the browser or on Wasmer Edge. A practical way to embed interpreter sandboxes in JS or Python apps; pick Wasmtime for a pure engine and a hosted VM sandbox for full Linux.
just-bash vs alternatives
| Sandbox | Isolation | Open source | Self-host / BYOC | Cold start (vendor) | Max session | Snapshots / pause | GPU | SDKs |
|---|---|---|---|---|---|---|---|---|
| just-bash | In-process interpreter | Yes | Yes / No | Not documented | Not documented | No / No | No | JavaScript/TypeScript |
| Pyodide | CPython in Wasm | Yes | Yes / No | Not documented | Not documented | No / No | No | JavaScript/TypeScript, Python |
| Vercel Sandbox | Firecracker microVM | No | No / No | Milliseconds (claim) | 24 h (Pro) | Yes / Yes | Not documented | JavaScript/TypeScript, Python |
| Wasmer | Wasm sandbox | Yes | Yes / No | Not documented | Not documented | Not documented / Not documented | No | CLI, JavaScript/TypeScript, Python, Rust, Swift |
| WebContainers | Browser tab (WebAssembly) | No | No / No | ms (claimed) | Not documented | No / No | No | JavaScript/TypeScript |
Frequently asked questions
Cite this page
Agent Sandboxes. (2026). just-bash alternatives. agentsandboxes.org. Last reviewed November 9, 2026. https://agentsandboxes.org/alternatives/just-bash/
Found an error or a missing sandbox? Submit a correction — every entry links to the sources it relies on.