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
bashdeno install
Reads package.json, resolves the same dependencies, writes node_modules, and
creates deno.lock — seeded from any existing package-lock.json, yarn.lock,
bun.lock, or pnpm lockfile, so pins and integrity hashes carry over instead of
drifting.
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
bashdeno 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.
bashdeno 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.
Command equivalents
| Task | npm | Yarn | pnpm | Bun | Deno |
|---|---|---|---|---|---|
| Install all | npm install | yarn install | pnpm install | bun install | deno install |
| Add | npm i <p> | yarn add <p> | pnpm add <p> | bun add <p> | deno add <p> |
| Add dev | npm i -D <p> | yarn add -D <p> | pnpm add -D <p> | bun add -d <p> | deno add -D <p> |
| Remove | npm uninstall <p> | yarn remove <p> | pnpm remove <p> | bun remove <p> | deno remove <p> |
| CI install | npm ci | yarn install --immutable† | pnpm i --frozen-lockfile | bun install --frozen-lockfile | deno ci |
| Run script | npm run <s> | yarn <s> | pnpm <s> | bun run <s> | deno task <s> |
| Run binary | npx <p> | yarn dlx <p> | pnpm dlx <p> | bunx <p> | dx <p> |
| Outdated | npm outdated | yarn outdated‡ | pnpm outdated | bun outdated | deno outdated |
| Audit | npm audit | yarn npm audit† | pnpm audit | bun audit | deno audit |
| Why | npm ls <p> | yarn why <p> | pnpm why <p> | bun why <p> | deno why <p> |
| Run a file | node f.js | bun f.ts | deno f.ts | ||
| Run TS | ts-node f.ts | bun f.ts | deno f.ts | ||
| Watch | nodemon f.js | bun --watch f.ts | deno watch f.ts | ||
| Format | prettier | prettier | deno fmt | ||
| Lint | eslint | deno lint | |||
| Test | jest, vitest | bun test | deno test | ||
| Coverage | nyc, c8 | deno coverage | |||
| Type-check | tsc --noEmit | tsc | deno check | ||
| Bundle binary | pkg, nexe | bun build --compile | deno compile |
† Yarn Berry (v2+) spelling. Yarn Classic (v1) uses
yarn install --frozen-lockfile and yarn audit.
‡ 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:
bashdeno 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:
json{ "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.cjsis unused and.yarnrc.ymlresolver 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.
Per-tool details
references/FROM_NPM.md— lockfile seeding,node_moduleslayout, overridesreferences/FROM_YARN.md— Plug'n'Play, Berry vs Classic, workspacesreferences/FROM_PNPM.md—pnpm-workspace.yaml,catalog:, patchesreferences/FROM_BUN.md— Bun API translation,bunfig.tomlreferences/NODE_APIS.md—node:built-ins,DENO_COMPAT, CJS/ESM
Further reading
- https://docs.deno.com/runtime/migrate/ — official migration guides
- https://docs.deno.com/runtime/fundamentals/node/ — Node and npm compatibility
- https://docs.deno.com/runtime/reference/node_apis/ — per-module Node API status
