What package version does @next specify for npm?

next is a version or tag published in your reference npm registry

npm install installs a package.

A package is:

...
d) a <name>@<version> that is published on the registry (see npm-registry) with (c)
e) a <name>@<tag> (see npm-dist-tag) that points to (d)
...

You can view the version that each dist-tag points to by running the following commands:

npm view <package_name> dist-tags
npm dist-tags ls <package_name>

e.g. for the react npm package:

npm view react dist-tags

Output:

{
  latest: '17.0.2',
  next: '18.0.0-rc.0-next-3dc41d8a2-20211223',
  experimental: '0.0.0-experimental-3dc41d8a2-20211223',
  beta: '18.0.0-beta-24dd07bd2-20211208',
  rc: '18.0.0-rc.0'
}

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