What is the difference between exports and module.exports in Node.js?

Direct answer

module.exports is the actual export object require() returns; exports is a shorthand reference to it — reassigning exports breaks the link, but adding properties to exports works; set module.exports to a function or class when that is the whole export.

At load time Node sets exports = module.exports — they start as the same object. Interview questions often trap candidates who reassign exports to a new object.

Pattern	Works?	Why
exports.foo = 1	Yes	Mutates shared module.exports object
module.exports = { foo: 1 }	Yes	Replaces export wholesale
exports = { foo: 1 }	No	Rebinds local exports variable only
module.exports = function() {}	Yes	Single function export pattern

ESM equivalent — export default / export { named } — no module.exports.
Barrel files — re-export from index.cjs: module.exports = require('./impl');

exports-pattern.cjs

// Correct: attach properties
exports.parse = (s) => JSON.parse(s);

// Correct: replace entire export
module.exports = function createServer() {
  return http.createServer();
};

// Wrong — importers still get old object
// exports = { parse: (s) => JSON.parse(s) };

// require('./exports-pattern.cjs') returns createServer function