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Licensecheck Build Status

A quick way to see the licenses of modules you depend on, recursively.

There are a few other tools that do this too, but this one aims to be particularly robust to minimize manual work. It checks multiple palaces for licenses (package.json, license files, and READMEs), and then flexibly matches the license strings and normalizes the results so they are standardized licenses whenever possible, to ease legal review.


Run npm -g install licensecheck.


licensecheck [-m/--missing-only] [-h/--highlight regexp] [optional dir]
    -m / --missing-only : only list licenses that are unspecified
    -f / --flat : write flattened list of dependencies
    --tsv : write flattened list of dependencies, tab-separated, without coloring (suitable for parsing)
    -h regexp / --highlight regexp : highlight licenses entries that match the regular expression (case insensitive)
    --dev : include development dependencies
    --opt : include optional dependencies
    --once : write each dependency only once, even if it appears in several places in the dependency tree
    --hide <license1,license2,...> : Hide packages with given licenses


$ licensecheck
└─ licensecheck (0.2.2) ── zlib License ( ── package.json
   ├─ colors (0.6.2) ── MIT License ( ── node_modules/colors/MIT-LICENSE.txt
   ├─ markdown (0.5.0) ── MIT ( ── node_modules/markdown/package.json
   │  └─ nopt (2.1.2) ── MIT ( ── node_modules/markdown ~ nopt/package.json
   │     └─ abbrev (1.0.5) ── MIT ( ── node_modules/markdown ~ nopt ~ abbrev/package.json
   ├─ spdx-license-list (1.1.0) ── MIT License ( ── node_modules/spdx-license-list/package.json
   └─ treeify (1.0.1) ── MIT ( ── node_modules/treeify/package.json
$ licensecheck --flat
abbrev (1.0.5) ── MIT ( ── node_modules/markdown ~ nopt ~ abbrev/package.json
colors (0.6.2) ── MIT License ( ── node_modules/colors/MIT-LICENSE.txt
licensecheck (0.2.2) ── zlib License ( ── package.json
markdown (0.5.0) ── MIT ( ── node_modules/markdown/package.json
nopt (2.1.2) ── MIT ( ── node_modules/markdown ~ nopt/package.json
spdx-license-list (1.1.0) ── MIT License ( ── node_modules/spdx-license-list/package.json
treeify (1.0.1) ── MIT ( ── node_modules/treeify/package.json
$ licensecheck --tsv | cut -f2 | sort -u
MIT License (
zlib License (


Occasionally, packages will not have a license that can be detected. If you manually verify the license and wish to save this, you can add a licenses.json file in the top-level directory that contains details of the licenses. The format (which may include comments) is:

/* This file holds overrides used by the licensecheck tool, handling dependencies
   with manually verified licenses that were not uploaded to npm. */
  "uglify-js": { "license": "BSD-2-Clause", "url": "" },
  "base64id": { "license": "MIT", "url": "" },

Use SPDX license names in this file.

How it works

Licensecheck looks for license information in the following order:

  1. package.json "license" field
  2. package.json "licenses" field
  3. file with license in its name
  4. file with readme or copying in its name a. if the filename ends in .md or .markdown, parses markdown looking for a section with license in its name b. otherwise checks for license in its text

The results are then used to match against known licenses. License information is matched by both signature and by name. Signatures are simply based on the text of a license (ignoring case, whitespace, and punctuation). These are in the license-files folder. If the full license is just a name (e.g. just "MIT" appearing in any of the above locations), then it is matched against the identifier used by the SPDX license list. Package licenses that include explicit URLs are always preserved (i.e. not normalized).


This is pretty hacky and experimental, so use at your own risk.


Licensecheck is open source software under the zlib license.


I am not a lawyer. The output of this app should not be considered legal advice and is not guaranteed to be accurate.