JavaScript Sandboxing Research

Simon Willison’s Weblog Subscribe Sponsored by: WorkOS — The infrastructure fast-growing B2B companies use to sell to Enterprise. RESEARCH JavaScript Sandboxing Research — Analyzing current JavaScript sandboxing options for running untrusted code, this research compares core approaches in Node.js (including worker_threads, node:vm, and the Permission Model), prominent npm packages (isolated-vm, vm2), and alternative engines like quickjs-emscripten. Aaron Harper wrote about Node.js worker threads, which inspired me to run a research task to see if they might help with running JavaScript in a sandbox. Claude Code went way beyond my initial question and produced a comparison of isolated-vm, vm2, quickjs-emscripten, QuickJS-NG, ShadowRealm, and Deno Workers. Posted 22nd March 2026 at 7:53 pm Recent articles Experimenting with Starlette 1.0 with Claude skills - 22nd March 2026 Profiling Hacker News users based on their comments - 21st March 2026 Thoughts on OpenAI acquiring Astral and uv/ruff/ty - 19th March 2026 This is a beat by Simon Willison, posted on 22nd March 2026. sandboxing 36 javascript 746 nodejs 68 claude-code 99 Monthly briefing Sponsor me for $10/month and get a curated email digest of the month's most important LLM developments. Pay me to send you less! Sponsor & subscribe Disclosures Colophon © 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024 2025 2026