CodeSandbox Review 2026

CodeSandbox is a cloud development and code-execution platform — now part of Together AI — built around the Sandbox SDK and Firecracker microVMs with 2-second startup for AI agents and dev environments.

CodeSandbox, the cloud IDE that pioneered in-browser React prototyping, is now part of Together AI (announced banner: 'CodeSandbox is now part of Together AI! We have joined forces to launch CodeSandbox SDK and bring code interpretation to generative AI.'). The 2026 positioning leans hard into AI agent infrastructure: Sandbox SDK lets you programmatically spin up isolated dev environments for code interpretation, eval harnesses, and agent task execution; Sandpack provides live coding in the browser; and the classic Code in Sandboxes experience still ships for prototyping and learning. The microVM architecture (based on Firecracker) gives 2-second VM startup, snapshot-based resume after periods of inactivity, customizable hibernation, and 'millions of concurrent VMs' for AI agent workloads — including the ability to run agents in parallel without interference and fork sandboxes for A/B testing. The homepage cites templates, '0 million+ users,' '0+ repositories connected,' and '0.0 billion+ lines of code' (numbers obfuscated as variables in the static HTML). Pricing: a free tier exists ('Start for free'), but the public pricing page currently returns HTTP 403 to crawlers — confirm the current Pro/Enterprise pricing matrix on codesandbox.io/pricing in a real browser before quoting numbers to a customer. Compare with <a href="/tools/replit">Replit</a> for a full IDE + Agent, <a href="/tools/e2b">E2B</a> for an AI-agent-native code interpreter, <a href="/tools/daytona">Daytona</a> for self-hostable dev environments, and <a href="/tools/modal-labs">Modal Labs</a> for serverless Python compute.