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Give me a string and I'll tell you if it's a valid npm package name.

This package exports a single synchronous function that takes a string as input and returns an object with two properties:

  • validForNewPackages :: Boolean
  • validForOldPackages :: Boolean


Naming Rules

Below is a list of rules that valid npm package name should conform to.

  • package name length should be greater than zero
  • all the characters in the package name must be lowercase i.e., no uppercase or mixed case names are allowed
  • package name can consist of hyphens
  • package name must not contain any non-url-safe characters (since name ends up being part of a URL)
  • package name should not start with . or _
  • package name should not contain any spaces
  • package name should not contain any of the following characters: ~)('!*
  • package name cannot be the same as a node.js/io.js core module nor a reserved/blacklisted name. For example, the following names are invalid:
    • http
    • stream
    • node_modules
    • favicon.ico
  • package name length cannot exceed 214


Valid Names

var validate = require("validate-npm-package-name")


All of the above names are valid, so you'll get this object back:

  validForNewPackages: true,
  validForOldPackages: true

Invalid Names

validate(" leading-space:and:weirdchars")

That was never a valid package name, so you get this:

  validForNewPackages: false,
  validForOldPackages: false,
  errors: [
    'name cannot contain leading or trailing spaces',
    'name can only contain URL-friendly characters'

Legacy Names

In the old days of npm, package names were wild. They could have capital letters in them. They could be really long. They could be the name of an existing module in node core.

If you give this function a package name that used to be valid, you'll see a change in the value of validForNewPackages property, and a warnings array will be present:



  validForNewPackages: false,
  validForOldPackages: true,
  warnings: [
    "name can no longer contain capital letters",
    "name can no longer contain more than 214 characters"


npm install
npm test