Yes, npm uses more space than what is necessary, but luckily disk space is cheap. That said, npm does optimize the disk space usage a bit. If I have package A w

Yes, npm uses more space than what is necessary, but luckily disk space is cheap. That said, npm does optimize the disk space usage a bit. If I have package A which depends on packages B and C, both of which need D, then (if the versions match), D will be installed only once.