What is the difference between npm-shrinkwrap.json and package-lock.json?

The files have exactly the same content, but there are a handful of differences in how npm handles them, most of which are noted on the docs pages for package-lock.json and npm-shrinkwrap.json:

• package-lock.json is never published to npm, whereas npm-shrinkwrap is by default
• package-lock.json files that are not in the top-level package are ignored, but shrinkwrap files belonging to dependencies are respected
• npm-shrinkwrap.json is backwards-compatible with npm versions 2, 3, and 4, whereas package-lock.json is only recognized by npm 5+

You can convert an existing package-lock.json to an npm-shrinkwrap.json by running npm shrinkwrap.

Thus:

• If you are not publishing your package to npm, the choice between these two files is of little consequence. You may wish to use package-lock.json because it is the default and its name is clearer to npm beginners; alternatively, you may wish to use npm-shrinkwrap.json for backwards compatibility with npm 2-4 if it is difficult for you to ensure everyone on your development team is on npm 5+. (Note that npm 5 was released on 25th May 2017; backwards compatibility will become less and less important the further we get from that date, as most people will eventually upgrade.)

• If you are publishing your package to npm, you have a choice between:

  1. using a package-lock.json to record exactly which versions of dependencies you installed, but allowing people installing your package to use any version of the dependencies that is compatible with the version ranges dictated by your package.json, or
  2. using an npm-shrinkwrap.json to guarantee that everyone who installs your package gets exactly the same version of all dependencies

  
  The official view described in the docs is that option 1 should be used for libraries (presumably in order to reduce the amount of package duplication caused when lots of a package's dependencies all depend on slightly different versions of the same secondary dependency), but that option 2 might be reasonable for executables that are going to be installed globally.

Explanation from NPM Developer:

The idea is definitely for package-lock.json to be the Latest and Greatest in shrinkwrap technology, and npm-shrinkwrap.json to be reserved for those precious few folks out there who care very much about their libraries having an exact node_modules -- and for people who want CI using npm@>=2 to install a particular tree without having to bump its npm version.

The new lockfile ("package-lock.json") shares basically all of the same code, the exact same format as npm-shrinkwrap (you can rename them between one another!). It's also something the community seems to understand: "it has a lockfile" seems to click so much faster with people. Finally, having a new file meant that we could have relatively low-risk backwards-compat with shrinkwrap without having to do weird things like allow-publication mentioned in the parent post.