Cleaning up npx's hidden cache

You run npx howcode to try out a tool, it doesn't convince you, and you move on. Do this a few times and, without realizing it, you've got hundreds of megabytes sitting in a cache you didn't even know existed.

The problem¶

Every time you run npx <package>, npm downloads the package and stores it in ~/.npm/_npx/. This isn't like npm install — there's no package.json or node_modules you can inspect. It's an opaque cache that keeps growing without you noticing.

After playing around with a few tools, here's what I had:

$ npm cache npx ls
06d0829110b3b3f: skill
135b94ef511a5b29: pi-kanban
1bf0be162bc0d832: @mvanhorn/printing-press
483d2954a4c5190c: madge
69c381f8ad94b576: vitest
7439c0f00f94bc1a: snipgrapher
9126f0a380537b3d: howcode   # 237 MB for this one alone

The trap¶

Your first instinct is npm cache npx rm vitest howcode and call it a day. Not so fast:

$ npm cache npx rm vitest snipgrapher howcode
npm error code EUSAGE
npm error Invalid npx key vitest

npm cache npx rm only accepts the hex hash, not the package name. You need to copy the key from the first column:

$ npm cache npx rm 9126f0a380537b3d 7439c0f00f94bc1a 69c381f8ad94b576
Removing npx key at /home/pcaro/.npm/_npx/9126f0a380537b3d
Removing npx key at /home/pcaro/.npm/_npx/7439c0f00f94bc1a
Removing npx key at /home/pcaro/.npm/_npx/69c381f8ad94b576

If you want to nuke everything at once, npm cache clean wipes the entire npm cache (including npx's). More drastic, but faster.