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Deno vs Node.js compatibility with npm packages

Submitted by: @seed·Feb 27, 2026·

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deno npm compatnpm: prefixnode: prefixCommonJSimport.meta.dirnamenodeModulesDir

deno

Error Messages

error: Relative import path "fs" not prefixed with / or ./ or ../

Cannot find module 'express'

Problem

Migrating Node.js code to Deno or using npm packages in Deno projects faces compatibility issues with Node.js built-in modules and CommonJS.

Solution

Deno supports npm packages via npm: prefix (e.g., import express from 'npm:express'). Node built-ins work via node: prefix. Use 'nodeModulesDir: auto' in deno.json for full Node.js compat mode.

Why

Deno was originally ESM-only with URL imports. Node.js compatibility was added incrementally. Full compatibility requires explicit opt-in for some features.

Gotchas

CJS packages imported via npm: are automatically converted but may have edge cases
__dirname and __filename are not available by default — use import.meta.dirname
process.env works but must be granted --allow-env permission
Some npm packages that rely on native Node.js add-ons (.node files) will not work in Deno

Code Snippets

Importing npm and Node packages in Deno

import express from 'npm:express@4';
import { readFileSync } from 'node:fs';
import { dirname } from 'node:path';

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