> ## Documentation Index
> Fetch the complete documentation index at: https://arizeai-433a7140.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# Deno

> Run simple TypeScript code evaluators locally inside the Phoenix server.

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  <img src="https://storage.googleapis.com/arize-phoenix-assets/assets/svgs/deno.svg" alt="Deno" className="invert-on-dark" style={{ height: '112px', flexShrink: 0 }} />

  <div>
    The **Deno** sandbox is a **local sandbox** for **simple TypeScript evaluators** — pure-logic checks like regex matches, JSON parsing, and scoring functions. It runs locally inside the Phoenix server, starts in milliseconds, and needs no credentials.
  </div>
</div>

Configure it from [Settings → Sandboxes](/docs/phoenix/settings/sandboxes).

## What it supports

The Deno sandbox runs your TypeScript in a locked-down local process. It is intentionally limited to **self-contained code**:

| Capability               | Supported?                             |
| :----------------------- | :------------------------------------- |
| Environment variables    | ❌ Not supported — use a hosted sandbox |
| Network access           | ❌ Not supported — use a hosted sandbox |
| Third-party dependencies | ❌ Not supported — use a hosted sandbox |

If your evaluator needs **any** of the above, it cannot run on Deno. Use a [hosted sandbox](/docs/phoenix/settings/sandboxes#local-vs-hosted-sandboxes) (E2B, Daytona, Vercel, or Modal) instead — those run each evaluation on an isolated remote VM with full support for environment variables, outbound network access, and installed packages.

## Running untrusted code

The Deno sandbox is tightly restricted, but it runs in the Phoenix server process, so it is **not a substitute for running untrusted code on isolated infrastructure**. The script shares CPU and memory with Phoenix, and the security boundary depends on Deno itself. If you need to evaluate code from sources you cannot verify, use a [hosted sandbox](/docs/phoenix/settings/sandboxes#local-vs-hosted-sandboxes).