Use when moving a Node.js, npm, Yarn, pnpm, or Bun project to Deno, or when adopting Deno incrementally in an existing JavaScript or TypeScript codebase. Covers using Deno as a drop-in package manager, running existing package.json scripts, CommonJS versus ESM, node_modules layout, lockfile migration, permissions, whether to adopt the built-in toolchain, and per-tool command equivalents.
Use when moving a Node.js, npm, Yarn, pnpm, or Bun project to Deno, or when adopting Deno incrementally in an existing JavaScript or TypeScript codebase. Covers using Deno as a drop-in package manager, running existing package.json scripts, CommonJS versus ESM, node_modules layout, lockfile migration, permissions, whether to adopt the built-in toolchain, and per-tool command equivalents.
license
MIT
metadata
{"author":"denoland","version":"1.0"}
Migrating to Deno
Requires Deno 2.9 or later. For general Deno usage once migrated, see the deno
skill.
Most Node projects already run under Deno
Deno reads an existing package.json, resolves the same npm packages, writes a
real node_modules, runs the same scripts, and supports node: built-ins.
TypeScript runs with no build step.
There is usually no code to change — only which binary you invoke. Don't
start by rewriting imports to jsr:, swapping dependencies for Deno-specific
ones, or restructuring directories. Proposing that is the most common way this
goes wrong.
Migrate in rungs
Each rung is independently useful and reversible. Stop wherever suits the
project; plenty of teams stop at rung 1.
Rung 1 — Deno as the package manager only
deno install
Reads package.json, resolves the same dependencies, writes , and
creates — seeded from any existing , ,
, or pnpm lockfile, so pins and integrity hashes carry over instead of
drifting.
node_modules
deno.lock
package-lock.json
yarn.lock
bun.lock
The app still runs under node; teammates are unaffected. Commit deno.lock
once verified. To back out: delete deno.lock and node_modules, then
npm install.
Rung 2 — Run it with Deno
deno run -A main.js # or: deno -A main.js
deno task build # runs scripts.build from package.json
Use -A here. The goal is confirming the program works, not designing a
permission policy — changing both at once makes failures ambiguous.
Rung 3 — Tighten permissions
Replace -A with the narrowest set that works: run it, read what it asks for,
grant exactly that.
deno run --allow-net=api.example.com --allow-read=./config --allow-env=PORT main.js
This buys something Node cannot offer, and is worth doing before deploying.
Rung 4 — Optionally, adopt the built-in toolchain
deno fmt for prettier, deno lint for eslint, deno test for jest or vitest,
deno check for tsc, deno watch for nodemon, deno compile for pkg.
Optional, and usually not worth it for an existing project. These are not
drop-in replacements; parity is incomplete, so this is a real migration, not a
config change. A project happy with prettier, eslint, and vitest should keep
them and use Deno as runtime and package manager only. Prefer the built-in tools
for new projects. If you do move an existing one, go a tool at a time.
‡ Yarn Classic only — Berry removed yarn outdated.
dx is a separate binary installed alongside Deno, and an alias for deno x.
It does not appear in the top-level deno --help output. Like npx, it runs
the package with the sandbox disabled.
The four things that actually break
Requires net access to "..." (or read, env, run)
Deno grants nothing by default. Add that specific permission, or -A while
still establishing the program works at all.
ReferenceError: require is not defined
A file containing CommonJS is being parsed as ESM. .cjs is always CommonJS,
.mjs always ESM; .js and .ts follow "type" in the nearest
package.json. For a CommonJS project, set "type": "commonjs".
A dependency is broken, or postinstall never ran
Lifecycle scripts don't run by default. Native addons notice immediately.
Approvals are recorded in the config file, so this is one-time:
deno approve-scripts # interactive picker
deno install --allow-scripts=npm:better-sqlite3 # or name them directly
A tool cannot find files inside node_modules
Deno's layout is pnpm-style: real files in node_modules/.deno/, exposed via
symlinks. Tools assuming npm's flat hoisted tree need:
{"nodeModulesLinker":"hoisted"}
What has no Deno equivalent
Say so rather than improvising a workaround that won't hold:
Yarn Plug'n'Play. Deno creates a real node_modules; .pnp.cjs is unused
and .yarnrc.yml resolver settings don't transfer.
yarn patch / pnpm patched dependencies. Vendor or fork.
overrides / resolutions. Pin via an import map entry instead.
Registry and resolver tuning in .npmrc / .yarnrc.yml.
Bun build features — macros, HTMLRewriter, HTML entrypoints.
