An E2B alternative with no sandbox server
The same Linux sandbox for agents and code, run on your visitor’s computer instead of your cloud bill.
Try it in your browser
npm i @uncontained/sdk yarn add @uncontained/sdk pnpm add @uncontained/sdk bun add @uncontained/sdk deno add npm:@uncontained/sdk Uncontained vs E2B, side by side
E2B runs sandboxes in Firecracker microVMs on a Linux 6.1 kernel, in E2B’s cloud, with templates for Claude Code, Codex and opencode.
| Capability | Uncontained | E2B |
|---|---|---|
| Where it runs | The visitor’s browser tab | E2B’s cloud |
| Sandbox server to run and pay for | None | Yes |
| Real Linux kernel | Yes, Linux 6.18 | Yes, Linux 6.1 |
| Claude Code, Codex, opencode | Yes | Yes, as templates |
| Restore a saved machine | 476 ms, Chrome | Resumes from a snapshot |
| Node and Bun without CPU emulation | Yes, on the browser’s JIT | Native, on their servers |
E2B facts are from E2B’s own pages, read on 10 November 2026.
When E2B is the better fit
E2B runs on servers: full x86 or arm Linux, public URLs, no browser limits and no download for the user. When code must run on your side, not the visitor’s, it is the right tool.
Questions about switching from E2B
Why run a sandbox in the browser instead of the cloud?
- Each visitor brings their own CPU and memory, so there is no sandbox server to scale or pay for, and their files stay on their computer.
Can coding agents run in it?
- Yes. Claude Code runs on native JS through the exec router; opencode and other Node or Bun agents run the same way.