Code Quality Rank: L5
Monthly Downloads: 0
Programming language: JavaScript
License: MIT License
Tags: Natural Language Processing     Detect     System     CLI     Bin     Guess     Writing     Language     Natural    
Latest version: v7.0.0

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Detect the language of text.

What’s so cool about franc?

  1. franc can support more languages(†) than any other library
  2. franc is packaged with support for 82, 187, or 403 languages
  3. franc has a CLI

† - Based on the UDHR, the most translated document in the world.

What’s not so cool about franc?

franc supports many languages, which means it’s easily confused on small samples. Make sure to pass it big documents to get reliable results.


This package is ESM only: Node 12+ is needed to use it and it must be imported instead of required.


npm install franc

This installs the franc package, with support for 187 languages (languages which have 1 million or more speakers). franc-min (82 languages, 8m or more speakers) and franc-all (all 403 possible languages) are also available. Finally, use franc-cli to install the CLI.

Browser builds for franc-min, franc, and franc-all are available on GitHub Releases.


This package exports the following identifiers: franc, francAll. There is no default export.

import {franc, francAll} from 'franc'

franc('Alle menslike wesens word vry') // => 'afr'
franc('এটি একটি ভাষা একক IBM স্ক্রিপ্ট') // => 'ben'
franc('Alle menneske er fødde til fridom') // => 'nno'

franc('') // => 'und' (language code that stands for undetermined)

// You can change what’s too short (default: 10):
franc('the') // => 'und'
franc('the', {minLength: 3}) // => 'sco'
console.log(francAll('Considerando ser essencial que os direitos humanos'))


  [ 'por', 1 ],
  [ 'glg', 0.771284519307895 ],
  [ 'spa', 0.6034146900423971 ],
  [ 'cat', 0.5367251059928957 ],
  [ 'src', 0.47461899851037015 ],
  ... 122 more items ]
  francAll('Considerando ser essencial que os direitos humanos', {
    only: ['por', 'spa']


[ [ 'por', 1 ], [ 'spa', 0.6034146900423971 ] ]
  francAll('Considerando ser essencial que os direitos humanos', {
    ignore: ['src', 'glg']


[ [ 'por', 1 ],
  [ 'spa', 0.6034146900423971 ],
  [ 'cat', 0.5367251059928957 ],
  [ 'ita', 0.4740460639394981 ],
  [ 'fra', 0.44757648676521145 ],
  ... 120 more items ]



npm install franc-cli --global


CLI to detect the language of text

Usage: franc [options] <string>


  -h, --help                    output usage information
  -v, --version                 output version number
  -m, --min-length <number>     minimum length to accept
  -o, --only <string>           allow languages
  -i, --ignore <string>         disallow languages
  -a, --all                     display all guesses


# output language
$ franc "Alle menslike wesens word vry"
# afr

# output language from stdin (expects utf8)
$ echo "এটি একটি ভাষা একক IBM স্ক্রিপ্ট" | franc
# ben

# ignore certain languages
$ franc --ignore por,glg "O Brasil caiu 26 posições"
# src

# output language from stdin with only
$ echo "Alle mennesker er født frie og" | franc --only nob,dan
# nob

Supported languages

Package Languages Speakers
franc-min 82 8M or more
franc 187 1M or more
franc-all 403 -

Language code

Note that franc returns ISO 639-3 codes (three letter codes). Not ISO 639-1 or ISO 639-2. See also GH-10 and GH-30.

To get more info about the languages represented by ISO 639-3, use iso-639-3. There is also an index available to map ISO 639-3 to ISO 639-1 codes, iso-639-3/to-1.json, but note that not all 639-3 codes can be represented in 639-1.


Franc has been ported to several other programming languages.

The works franc is derived from have themselves also been ported to other languages.


Franc is a derivative work from guess-language (Python, LGPL), guesslanguage (C++, LGPL), and Language::Guess (Perl, GPL). Their creators granted me the rights to distribute franc under the MIT license: respectively, Kent S. Johnson, Jacob R. Rideout, and Maciej Ceglowski.


[MIT][] © Titus Wormer

<!-- Definitions -->

*Note that all licence references and agreements mentioned in the franc README section above are relevant to that project's source code only.