node_modules Layouts

Three folder layouts can make one graph visible to Node.js 2,131 (5). npm 1 2,036 and 2 used the nested layout, where every package gets its own private node_modules; npm 3 (2015) switched to the flat, hoisted layout. pnpm 69,400 made the symlinked layout popular: a hidden store holds one folder per version, and symlinks re-create each package's declared dependencies and nothing else.

npm can still produce all three through its install-strategy setting (hoisted, nested, shallow and linked), so you can compare them on BookNest without changing tools.

cd ~/v5-ch1 && mkdir layouts
for s in hoisted nested linked; do
  mkdir layouts/$s && cp booknest/package.json layouts/$s/ && cd layouts/$s
  npm install --install-strategy=$s --no-audit --no-fund >/dev/null 2>&1
  copies=$(find node_modules -type f -regextype egrep \
    -regex '.*node_modules/(@[^/]+/)?[^/]+/package.json' | wc -l)
  echo "$s: $copies copies, $(ls node_modules | wc -l) top-level, $(du -sh node_modules | cut -f1)"
  cd ~/v5-ch1
done

hoisted: 82 copies, 79 top-level, 5.3M
nested: 98 copies, 2 top-level, 6.7M
linked: 80 copies, 2 top-level, 6.3M

Nested stores 98 copies of 80 packages, up to seven node_modules levels deep, the paths that once broke Windows' 260-character limit. linked, npm's version of pnpm's layout, keeps packages in node_modules/.store and looks larger than hoisted only because its 154 extra folders each take a disk block (the files total 2.6 MB in both). npm 11.18.0 made linked stable, so install-strategy=linked in .npmrc catches phantom dependencies without pnpm, though only pnpm's store shares files between projects (Global Store and Hard Links).