What is the “module” package.json field for?

Question

I\'ve seen some npm packages (vue for example) have a pkg.module field in their package.json. Is \"module\" an official npm property or is this a c

Answer 1

This is used by bundler tools for ESM (ECMAScript Module) detection. The Rollup documentation says it pretty well:

If your package.json file also has a module field, ES6-aware tools like Rollup and webpack 2 will import the ES6 module version directly.

This article on Rollup 1.0 says it another way:

The main field makes sure that Node users using require will be served the UMD version. The module field is not an official npm feature but a common convention among bundlers to designate how to import an ESM version of our library.

Further discussion of pkg.module is on the Rollup Github Wiki and the webpack Docs.