npm-outdated

Check for outdated packages

npm outdated [[<@scope>/] …]

This command will check the registry to see if any (or, specific) installed packages are currently outdated.

In the output:

wanted is the maximum version of the package that satisfies the semver range specified in package.json. If there's no available semver range (i.e. you're running npm outdated --global, or the package isn't included in package.json), then wanted shows the currently-installed version.
latest is the version of the package tagged as latest in the registry. Running npm publish with no special configuration will publish the package with a dist-tag of latest. This may or may not be the maximum version of the package, or the most-recently published version of the package, depending on how the package's developer manages the latest dist-tag.
location is where in the dependency tree the package is located. Note that npm outdated defaults to a depth of 0, so unless you override that, you'll always be seeing only top-level dependencies that are outdated.
package type (when using --long / -l) tells you whether this package is a dependency or a devDependency. Packages not included in package.json are always marked dependencies.
homepage (when using --long / -l) is the homepage value contained in the package's package.json
Red means there's a newer version matching your semver requirements, so you should update now.
Yellow indicates that there's a newer version above your semver requirements (usually new major, or new 0.x minor) so proceed with caution.

An example

$ npm outdated
Package Current Wanted Latest Location
glob 5.0.15 5.0.15 6.0.1 test-outdated-output
nothingness 0.0.3 git git test-outdated-output
npm 3.5.1 3.5.2 3.5.1 test-outdated-output
local-dev 0.0.3 linked linked test-outdated-output
once 1.3.2 1.3.3 1.3.3 test-outdated-output

With these dependencies:

{
“glob”: “^5.0.15”,
“nothingness”: “github:othiym23/nothingness#master”,
“npm”: “^3.5.1”,
“once”: “^1.3.1”
}

A few things to note:

glob requires ^5, which prevents npm from installing glob@6, which is outside the semver range.
Git dependencies will always be reinstalled, because of how they're specified. The installed committish might satisfy the dependency specifier (if it's something immutable, like a commit SHA), or it might not, so npm outdated and npm update have to fetch Git repos to check. This is why currently doing a reinstall of a Git dependency always forces a new clone and install.
npm@3.5.2 is marked as "wanted", but "latest" is npm@3.5.1 because npm uses dist-tags to manage its latest and next release channels. npm update will install the newest version, but npm install npm (with no semver range) will install whatever's tagged as latest.
once is just plain out of date. Reinstalling node_modules from scratch or running npm update will bring it up to spec.

Configuration
json

Default: false
Type: Boolean

Show information in JSON format.
long

Default: false
Type: Boolean

Show extended information.
parseable

Default: false
Type: Boolean

Show parseable output instead of tree view.
global

Default: false
Type: Boolean

Check packages in the global install prefix instead of in the current project.
depth

Default: 0
Type: Int

Max depth for checking dependency tree.