Get started with Deno

Deno (/ˈdiːnoʊ/, pronounced dee-no) is an open source JavaScript, TypeScript, and WebAssembly runtime with secure defaults and a great developer experience. This page takes you from nothing to a running, tested project in a few minutes.

Why Deno? Jump to heading#

• Works with your existing Node.js projects. Drop Deno into a repo with package.json and node_modules and it just runs; mix npm: imports with native ES modules as you migrate.
• Modern module system. ES modules with URL imports, JSR for typed packages, and workspaces.
• TypeScript-first. Run .ts files directly. No tsc, no build step, no config.
• Secure by default. Code runs in a sandbox with no file, network, or environment access until you grant it.
• A full toolchain, no plumbing. Built-in formatter, linter, test runner, benchmarking, and a lot more. No devDependencies to wire up.

Using an AI coding agent? Jump to heading#

Paste this into Claude Code, Codex, Gemini CLI, OpenCode, Cursor, Pi, or whichever agent you use:

Read deno.com/agents.md and set up Deno in this project

deno.com/agents.md is a single page written for coding agents: what Deno is, the assumptions to unlearn if it already knows Node, and how to install Deno's agent skills so it keeps that context in every session. If you are asking an agent to bring an existing Node project across, it covers that too.

Install Deno Jump to heading#

Install the runtime with one command:

curl -fsSL https://deno.land/install.sh | sh

# pwsh
irm https://deno.land/install.ps1 | iex

Verify the install:

deno --version

See Installation for package managers, Docker, and other options.

Create a project Jump to heading#

Scaffold a new project with deno init:

deno init my_project

That creates a small, ready-to-run project:

my_project
├── deno.json      # project configuration: tasks, imports, lint/fmt settings
├── main.ts        # a tiny HTTP server built on Deno.serve
└── main_test.ts   # its tests

deno.json is where your tasks, dependencies, and tooling config live. Think package.json plus your tool configs, in one file.

Run it Jump to heading#

$ cd my_project
$ deno -N main.ts
Listening on http://localhost:8000/

Notice the -N (short for --allow-net). Deno is secure by default: code can't touch the network, filesystem, or environment until you grant it. Open the URL to see the response.

main.ts is TypeScript and it ran directly: no tsc, no build step. It's also built on the web-standard Deno.serve with Request/Response, so what you learn here is the platform, not a framework.

Test it Jump to heading#

The project ships with tests. Run them with deno test. The test runner is built in, so there's nothing to install:

$ deno test
running 2 tests from ./main_test.ts
returns html on / ... ok (12ms)
returns json on /api ... ok (0ms)

ok | 2 passed | 0 failed (15ms)

Add a dependency Jump to heading#

Pull in packages from npm or JSR with deno install:

deno install express            # any npm package, like npm install
deno install jsr:@std/assert    # the Deno standard library, on JSR

Then import and use them:

import { assertEquals } from "@std/assert";

assertEquals(1 + 1, 2);

Use the built-in toolchain Jump to heading#

Formatting, linting, and more come with the runtime, no setup needed:

deno fmt     # format your code
deno lint    # catch problems
deno task    # run scripts defined in deno.json

Next steps Jump to heading#

• Set up your editor. Autocomplete, inline errors, and formatting on save.
• Run code. Servers, tasks, web APIs, and debugging.
• Manage packages. Dependencies, workspaces, publishing.
• Migrate from Node.js. Bring an existing project across.
• Examples and tutorials. Ideas for what to build next.