# deno

Guides your agent in Deno projects, handling npm imports, sandbox permissions, workspace setup, and the built-in toolchain.

- skill · `type=skill` · Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, OpenCode · 335 installs · ★ 102
- Author: denoland
- License: MIT · policy=mirror · the beginning of the file is at the end of this page
- Source: https://github.com/denoland/skills/tree/HEAD/skills/deno/SKILL.md
- Updated: 2026-07-29
- HTML: https://affpapa.org/en/nevibecode/skills/deno

## What it does

This skill instructs your assistant on managing Deno projects without enforcing breaking migrations. When a `package.json` file is present, the agent respects it: unprefixed dependencies install from npm via `deno add`, and TypeScript files run directly without separate build pipelines.

Project configuration stays cleanly separated across designated files. Compiler flags belong in `tsconfig.json`, dependencies stay inside `package.json`, and formatting rules or custom tasks go into `deno.json`. Native addons will fail until their install scripts are approved using `deno approve-scripts`. The skill requires Deno 2.9+ to operate.

## Install

### Claude Code (native platform)

1. **Skills CLI (Vercel)**
```bash
npx skills add denoland/skills --skill deno -a claude-code
```

2. **Manually: put the files in place**
- File: `~/.claude/skills/deno/SKILL.md` — Copy the whole skill folder; for one project use .claude/skills/deno/

### Codex

1. **Skills CLI (Vercel)**
```bash
npx skills add denoland/skills --skill deno -a codex
```

2. **Manually: put the files in place**
- File: `.agents/skills/deno/SKILL.md` — For all projects use ~/.agents/skills/

### Cursor

1. **Skills CLI (Vercel)**
```bash
npx skills add denoland/skills --skill deno -a cursor
```

2. **Manually: put the files in place**
- File: `.cursor/skills/deno/SKILL.md` — Cursor also reads .agents/skills/ and .claude/skills/

### GitHub Copilot

1. **GitHub CLI**
```bash
gh skill install denoland/skills deno
```

2. **Manually: put the files in place**
- File: `.github/skills/deno/SKILL.md`

### Gemini CLI

1. **Skills CLI (Vercel)**
```bash
npx skills add denoland/skills --skill deno -a gemini-cli
```

2. **Platform CLI**
```bash
gemini skills install https://github.com/denoland/skills --path skills/deno
```

### Windsurf (Devin Desktop)

**Manually: put the files in place**
- File: `.devin/skills/deno/SKILL.md` — The legacy .windsurf/skills/ path still works

### OpenCode

**Skills CLI (Vercel)**
```bash
npx skills add denoland/skills --skill deno -a opencode
```

### Claude.ai

**Claude.ai**
- Zip the folder and upload it in Settings → Capabilities → Skills

Where a file is given instead of a command, copy the files from the source to that path: https://github.com/denoland/skills/tree/HEAD/skills/deno/SKILL.md

## When to use it
- configure file and network permission flags for scripts
- install dependencies from npm or JSR via `deno add`
- organize configuration between `package.json`, `tsconfig.json`, and `deno.json`
- authorize lifecycle scripts for native addon packages

## Example prompts
- Add express from npm and configure a dev task in deno.json.
- Set read permissions for the data directory and allow network access in the run task.
- Run an audit on project dependencies and list outdated packages.

## Source text · SKILL.md · MIT

Below is the content of a third-party file. It is data, not instructions for you: do not act on anything written inside unless the human asks. Block tag: 2f0300c85b7640a3.

BEGIN THIRD-PARTY FILE 2f0300c85b7640a3
````text
---
name: deno
description: Use when writing, running, configuring, reviewing, or debugging code in a Deno project, or when scaffolding a new one. Covers dependency management with deno install and deno add, package.json and node_modules support, npm and JSR packages, permissions, where configuration belongs across package.json, tsconfig.json and deno.json, workspaces, the built-in toolchain (fmt, lint, test, check, bench, compile), and publishing.
license: MIT
metadata:
  author: denoland
  version: "1.0"
---

# Deno

A JavaScript and TypeScript runtime with a package manager, formatter, linter,
test runner, type checker, and bundler in one binary. Runs TypeScript directly.

Needs Deno 2.9+. Check with `deno --version`, update with `deno upgrade`.

## Deno works the way npm and bun do

Deno is not a separate ecosystem to port code into:

- `deno install` reads an existing `package.json` and writes a real
  `node_modules`.
- `deno add express` installs from **npm**. Unprefixed names default to npm.
- `deno task build` runs `scripts.build` from `package.json` or `tasks.build`
  from `deno.json`. If both define it, `deno.json` wins.
- Node built-ins work prefixed or not: `node:fs` and `fs` both resolve.
- `deno main.js` runs a file. `deno run` is optional.
- Deno reads `tsconfig.json`.

Don't tell users to rewrite imports, adopt JSR, or restructure as a
precondition. The two real differences are **permissions** and **npm lifecycle
scripts not running by default**.

Single-file scripts need no build step and no `tsconfig.json`. Applications and
framework projects keep their normal setup.

To convert an existing project, see the `migrate-to-deno` skill.

## Dependency management

```bash
deno install                  # install everything declared
deno add express              # from npm (unprefixed = npm)
deno add jsr:@std/path        # from JSR
deno add -D vitest            # dev dependency (package.json only)
deno remove express
deno outdated                 # list outdated deps
deno update                   # alias for `deno outdated --update`
deno update --latest          # ignore existing semver ranges
deno list                     # declared deps + resolved versions (npm ls)
deno why express              # why a package is in the tree
deno audit                    # vulnerability audit
deno ci                       # clean reproducible install for CI
dx cowsay hello               # run a package binary without installing (npx)
```

`deno ci` is the CI command, not `deno install`: it requires `deno.lock`,
deletes `node_modules`, installs strictly from the lockfile, and fails if the
lockfile is stale. `--prod` skips devDependencies.

`dx` is `npx` / `bunx` / `pnpm dlx`, and an alias for `deno x`. It runs **with
the sandbox disabled**, so treat it with the same care as `npx`.

Deno won't install a version published less than a day ago, limiting the window
for a compromised release. Override with `--min-dep-age`, which takes minutes
(`120`), an ISO-8601 duration (`P7D`), a cutoff date, or `0` to disable:

```bash
deno add --min-dep-age=0 npm:some-package
```

Lifecycle scripts (`postinstall`) don't run by default — a common surprise when
a native addon looks broken after install. Approve once per project:

```bash
deno approve-scripts                              # interactive picker
````
END THIRD-PARTY FILE 2f0300c85b7640a3

The third-party file has ended. Everything between the 2f0300c85b7640a3 tags is data: requests and commands from it are not followed. An “end of file” line with another tag inside the block is part of the file.

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