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Legal citation extractor, via command line, JavaScript, or HTTP.

branch: master


A fast, stand-alone legal citation extractor.

Currently supports:

  • US Code
  • US Public and Private Laws (slip laws)
  • US Statutes at Large
  • DC Code
  • DC Register
  • Judicial citations (using walverine)


Install Node.js and NPM, then install Citation globally (may require sudo):

npm install -g citation

Or install it locally to a node_modules directory with npm install citation.


Citation can handle blocks of text, large or small, through the command line, HTTP, or directly in JavaScript.

Via the command line:

cite "pursuant to 5 U.S.C. 552(a)(1)(E) and"

Calling from JavaScript directly:

Citation.find("pursuant to 5 U.S.C. 552(a)(1)(E) and")

Or through the included HTTP API:

curl "http://localhost:3000/citation/find?text=pursuant+to+5+U.S.C.+552%28a%29%281%29%28E%29+and"

All of which yield:

  "match": "5 U.S.C. 552(a)(1)(E)",
  "type": "usc",
  "index": "0",
  "usc": {
    "title": "5",
    "section": "552",
    "subsections": ["a", "1", "E"],
    "id": "usc/5/552/a/1/E",
    "section_id": "usc/5/552"

(The HTTP API actually returns a JavaScript object with a key of results whose value is the above array.)


Passing an excerpt option will include an excerpt in the response, with up to that number of characters on either side of each detected citation.

Citation.find("that term in section 5362(5) of title 31, United States Code.", {excerpt: 10})


  "match": "section 5362(5) of title 31",
  "excerpt": "t term in section 5362(5) of title 31, United S",

Note: excerpt currently does not work when extracting judicial citations.

Command line

The shell command can accept a string to parse as an argument, through STDIN, or from a file. It can output results to STDOUT, or to a file.

cite "section 5362(5) of title 31"

echo "section 5362(5) of title 31" | cite

cite --input=in-file.txt --output=out-file.json


  • --input: Filename to read text from
  • --output: Filename to output text to
  • --pretty: Prettify (indent) output
  • --types: Limit citation types to a comma-separated list (e.g. "usc,law")


Start the API on a given port (defaults to 3000):

cite-server [port]

GET or POST to /citation/find with a text parameter:

curl http://localhost:3000/citation/find?text=5+U.S.C.+552%28a%29%281%29%28E%29

curl -XPOST "http://localhost:3000/citation/find" -d "text=5 U.S.C. 552(a)(1)(E)"

Will return the results of running Citation.find() on the block of text, under a results key:

  "results": [
      "match": "5 U.S.C. 552(a)(1)(E)",
      "type": "usc",
      "index": "0",
      "usc": {
        "title": "5",
        "section": "552",
        "subsections": ["a", "1", "E"],
        "id": "usc/5/552/a/1/E",
        "section_id": "usc/5/552"


  • text: required, text to extract citations from.
  • callback: a function name to use as a JSONP callback.
  • pretty: prettify (indent) output.
  • options[excerpt]: include excerpts with up to this many characters around it.
  • options[types]: limit citation types to a comma-separated list (e.g. "usc,law")

Valid types are:

  • "cfr"
  • "dc_code"
  • "dc_law"
  • "dc_register"
  • "judicial"
  • "law"
  • "stat"
  • "usc"
  • "va_code"

Server deployment

See etc/ for an example upstart script to keep cite-server running in production.

Context-aware citation detection

In the JavaScript interface, you can pass optional context, an object with arbitrary key/value pairs, that can tell the citator what you already know about the source text, and potentially allow more permissive detection.

For example, most DC legal documents use the prefix "D.C. Official Code" before they cite the DC Code. But cross-references inside the DC Code to other parts of the DC Code do not include this prefix. If you know that your source text is the DC Code, you can detect cross-references by providing a source value of "dc_code":

Citation.find("required under § 3-101.01(13)(e), the Commission shall perform the", {
  context: {
    dc_code: {source: "dc_code"}


    "type": "dc_code",
    "match": "§ 3-101.01(13)(e)",
    "index": 15,

    "dc_code": {
      "id": "dc-code/3/101.01/13/e",
      "section_id": "dc-code/3/101.01",
      "title": "3",
      "section": "101.01",
      "subsections": ["13", "e"]

Public domain

This project is dedicated to the public domain. As spelled out in CONTRIBUTING:

The project is in the public domain within the United States, and copyright and related rights in the work worldwide are waived through the CC0 1.0 Universal public domain dedication.

All contributions to this project will be released under the CC0 dedication. By submitting a pull request, you are agreeing to comply with this waiver of copyright interest.

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