Node "Must use import to load ES Module" - Fix require() of ESM in CI

This error means CommonJS code used require() on a package that ships only as ESM. On older Node, ESM cannot be loaded with require, so the call throws ERR_REQUIRE_ESM. It usually appears after a dependency went ESM-only.

What this error means

A require(...) of a dependency throws Error [ERR_REQUIRE_ESM]: Must use import to load ES Module. It typically follows upgrading a package (e.g. a utility library) to a major that dropped CommonJS.

Node output

Error [ERR_REQUIRE_ESM]: require() of ES Module
/app/node_modules/chalk/source/index.js from /app/index.js not supported.
Instead change the require of index.js to a dynamic import() which is
available in all CommonJS modules.

Common causes

A dependency became ESM-only

A package upgraded to a version that publishes only ESM. CommonJS require() of it fails on Node versions that do not allow requiring ESM.

Your code is CommonJS but consumes ESM-only deps

A CJS codebase that pulls in ESM-only libraries must use dynamic import() or move to ESM; static require will not work.

How to fix it

Use dynamic import or pin a CJS version

Load the ESM module with await import() from CommonJS, or pin the last CJS-compatible version.

JavaScript / Terminal

// CommonJS calling an ESM-only package
const chalk = (await import('chalk')).default;
// or pin the last CJS major:
// npm install chalk@4

Move the project to ESM

Set "type": "module" and convert require/module.exports to import/export.
Or pin ESM-only dependencies to their last CJS release as a stopgap.
Upgrade Node so newer require(esm) support is available where applicable.

How to prevent it

Track when dependencies go ESM-only and plan the migration.
Use dynamic import() from CommonJS for ESM-only packages.
Standardize on one module system for your package.