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last_modified 2026-07-02
title How to adopt Deno
description A low-risk, step-by-step path for introducing Deno to an existing Node.js codebase and team: start with tooling, add a CI check alongside Node, use Deno as your package manager, pilot a project, then switch the runtime.

You don't have to adopt Deno all at once, and you don't need the whole team on board to start. Deno is designed to slot into an existing Node.js and npm codebase one piece at a time. Each step below is independently useful and fully reversible, so you can stop at any point, keep your package.json, and still come out ahead.

This guide lays out a path from "try it on one file" to "team runtime," ordered from lowest risk to highest. Start at the top, go as far as makes sense, and follow the links for the mechanics of each step.

Step 1: Start with tooling, not the runtime

The safest place to start changes nothing about how your application runs. deno fmt and deno lint operate on your existing files, need no configuration, and don't affect runtime behavior:

deno fmt
deno lint

Because Deno is a single binary with no dependencies to install, a teammate can try these without adding anything to package.json or node_modules. This is the easiest thing to put in front of a skeptical team: it replaces prettier and eslint with one tool and zero config, and it touches nothing else.

Step 2: Add a Deno check to CI, alongside Node

Once formatting and linting are useful locally, add them as a job next to your existing Node jobs. Your build, test, and deploy steps stay exactly as they are:

jobs:
  deno-checks:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: denoland/setup-deno@v2
        with:
          deno-version: v2.x
      - run: deno fmt --check
      - run: deno lint

This is the first place the team sees Deno running in the pipeline, with no runtime risk. For more CI patterns, see Continuous integration.

Step 3: Use Deno as your package manager

The next step still leaves your app running on Node. deno install reads the same package.json, resolves the same npm packages, and writes a node_modules directory, just like npm install:

deno install

From here you can keep running the app with node and use Deno only as a faster, more secure package manager. For the full command mapping and the caveats to know, see the guide for the tool you're coming from: npm, Yarn, pnpm, or Bun.

Step 4: Run scripts and tests with Deno

With dependencies in place, you can start running things through Deno without committing the whole app to it. deno task runs the scripts in your package.json, the same way npm run does:

deno task start

You can also point deno test at a single test file or directory to see how it handles a small, low-stakes slice of your suite before moving the rest. Pick something contained here: a build script, an internal tool, or one folder of tests, rather than the whole application.

Step 5: Pilot a project, then switch the runtime

When the team is comfortable, run one project on the Deno runtime itself with deno run. Choose a low-stakes pilot first, such as a new internal service, a CLI, or a script, rather than your most important app. Because package.json still works and nothing is rewritten, you can revert by going back to node if you hit a snag.

The mechanics of running an existing project on Deno, including permissions, how CommonJS and ES modules are resolved, and the handful of errors most projects hit on first run, are covered in detail in the Migrate from Node.js guide. When the pilot is stable, roll the same steps out to larger apps.

Why this is safe to try

Each argument here is one you can hand to a teammate who isn't sold yet:

  • Reversible. You keep your package.json, and Deno reads it directly. Backing a step out means running npm or node again, with nothing to undo.
  • Incremental. Every step is valuable on its own. Tooling-only adoption is a complete, useful outcome even if you never switch the runtime.
  • No lock-in. Deno doesn't require rewriting your code or maintaining a parallel config. The same repository keeps working under both tools while you decide.

Next steps