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# CLD - Compact Language Detector
This package contains the CLD (Compact Language Detection) library, extracted from the source code for Google's Chromium library at [](, specifically revision 105735. The original extraction was done by [Mike McCandless]( and was altered to improve the build and packaging as well as add new bindings for various languages.
The LICENSE is the same as Chromium's LICENSE and is included in the LICENSE file for reference.
# Installing the C++ library
## Prerequisites
Building the C++ library requires a C++ compiler (duh) as well as `pkg-config` so future programs can locate the needed dependancies.
## Building
The shared C++ library can be built from source using the following commands:
$ git clone git://
$ cd cld
$ ./configure
$ make
$ make check # optional. Runs the tests
## Installing
Once built from source:
$ make install
Or, Mac OSX users of Homebrew can build and install via:
$ brew install
# Ports
None of the ports are 100% completed yet but the preliminary APIs are introduced below
## Ruby
### Prerequisites
The `libcld` C++ library must be installed (see above)
### Installing
# 'gem install ...' in the near future
$ git clone
$ cd cld/ports/ruby
$ rake gem
$ gem install pkg/*gem
### Example
require 'CLD'
require 'pp' # just for illustration
cld =
res = cld.detect_language('I am the very measure of a modern major general')
pp res
@language=#<CLD::Language:0x007fb7728b66a0 @code="en", @name="ENGLISH">,
#<CLD::Language:0x007fb7728b6740 @code="en", @name="ENGLISH">,
### Documentation
Full RDoc documentation is at []( and
includes even more examples.
## Node
### Prerequisites
The `libcld` C++ library must be installed (see above). Tested with node version `10.0.26`.
### Installing
$ git clone
$ cd cld/ports/node
$ make -f Makefile.example test
$ npm install /PATH/FOR/CLD/cld/ports/node
### Example
Assuming you're in `/PATH/FOR/YOUR/PROJECT` above:
var LanguageDetector = require("cld/cld.node").LanguageDetector;
var detector = new LanguageDetector();
// Sync - Returns two letter language code of the most likely candidate language
var simpleResult = detector.detectSync("This is my sample text");
// Returns 'en' in this case
// Async - Returns detailed result structure
detector.detect("This is my sample text", function(result) {
// 'result' contains:
// { languageCode: 'en',
// reliable: false,
// details:
// [ { languageCode: 'en', normalizedScore: 20.25931928687196, percentScore: 64 },
// { languageCode: 'fr', normalizedScore: 8.221993833504625, percentScore: 36 },
// { languageCode: 'un', normalizedScore: 0, percentScore: 0 } ] }
### Documentation
Both the `detectSync` and `detect` methods take an option second parameter that is a hash of options. The available options (and defaults) are:
* `tld` (none): The TLD of the domain that the data came from. This is used as a hint for some ambiguous languages, for example the following snippet from there tests:
var detector = new LanguageDetector();
var ambig = " 常用漢字 ";
detector.detectSync(ambig) #=> "zh-TW"
detector.detectSync(ambig, { tld: "cn" }) #=> "zh"
detector.detectSync(ambig, { tld: "jp" }) #=> "ja"
* `html` (`false`): The string to be processed HTML. If this is the case then markup will be ignored in the calculations.
* `allowExtendedLanguages` (`true`): Return language from outside of the core set of supported languages (where wuality is not as good)
* `pickSummaryLanguage` (`false`): If true then the summary language may not be the top match, based on some other factors.
* `skipWeakMatches` (`false`): Include weak matches in the results
## Java
As a JNI library the Java port may require some environment settings to work correctly. For example on a fresh Ubuntu install I needed to install the Oracle JDK, set `JAVA_HOME` and `LD_LIBRARY_PATH` for linking and compilation to work correctly.
### Prerequisites
The `libcld` C++ library must be installed (see above). See the notes above about compilation and runtime linker environments.
### Installing
# Maven repository information in the future
$ git clone
$ cd cld/ports/java
# mvn test (optional)
$ mvn install
### Example
CompactLanguageDetector compactLanguageDetector = new CompactLanguageDetector();
LanguageDetectionResult result = compactLanguageDetector.detect("This is my sample text");
if (result.isReliable()) {
// getProbableLocale returns a java.util.Locale
System.out.println("Pretty sure that's " + result.getProbableLocale().getDisplayName());
} else {
for (LanguageDetectionCandidate candidate : result.getCandidates()) {
System.out.println("Maybe it's " + candidate.getLocale().getDisplayName());
### Documentation
Full Javadocs are at [](
## Python
### Prerequisites
The `libcld` C++ library must be installed (see above)
### Installing
$ git clone
$ cd cld/ports/python
$ make install # This will prompt for your password
### Example
import cld
detectedLangName, detectedLangCode, isReliable, textBytesFound, details = cld.detect("This is my sample text", pickSummaryLanguage=True, removeWeakMatches=False)
print ' detected: %s' % detectedLangName
print ' reliable: %s' % (isReliable != 0)
print ' textBytes: %s' % textBytesFound
print ' details: %s' % str(details)
# The output look lie so:
# detected: ENGLISH
# reliable: True
# textBytes: 25
# details: [('ENGLISH', 'en', 64, 20.25931928687196), ('FRENCH', 'fr', 36, 8.221993833504625)]
### Documentation
Once you've compiled & installed the Python bindings detection is easy.
First, you must get your content (plain text or HTML) encoded into UTF8 bytes. Then, detect like this:
topLanguageName, topLanguageCode, isReliable, textBytesFound, details = cld.detect(bytes)
The code and name of the top language is returned. isReliable is True
if the top language is much better than 2nd best language.
textBytesFound tells you how many actual bytes CLD analyzed (after
removing HTML tags, collapsing areas of too-many-spaces, etc.).
details has an entry per top 3 languages that matched, that includes
the percent confidence of the match as well as a separate normalized
The detect method takes optional params:
* `isPlainText` (default is False): set to True if you know your bytes
don't have any XML/HTML markup
* `includeExtendedLanguages` (default is True): set to False to
exclude "extended" languages added by Google
* `hintTopLevelDomain` (default is None): set to the last part of the
domain name that the content came from (for example if the URL was, pass the string 'cz'). This gives a
hint that can bias the detector somewhat.
* `hintLanguageCode` (default is None): set to the possible language.
For example, if the web-server declared the language, or the
content itself embedded an http-equiv meta tag declaring the
language, pass this (for example, "it" for Italian). This gives a
hint that can bias the detector somewhat.
* `hintEncoding` (default is None): set to the original encoding of
the content (note you still must pass UTF-8 encoded bytes). This
gives a hint that can bias the detector somewhat. NOTE: this is
currently not working.
* `pickSummaryLanguage` (default is False): if False, CLD will always
return the top matching language as the answer. If True, it will
sometimes pick 2nd or 3rd match (for example, if English and X
match, where X (not UNK) is big enough, assume the English is
boilerplate and return X). In simple testing accuracy seems to
suffer a bit (XX to YY %) when this is True so I've defaulted to
* `removeWeakMatches` (default is True): if a match isn't strong
enough, delete it. This ensures some amount of confidence when a
language is returned.
The module exports these global constants:
* `cld.ENCODINGS`: list of the encoding names CLD recognizes (if you
provide hintEncoding, it must be one of these names).
* `cld.LANGUAGES`: list of languages and their codes (if you provide
hintLanguageCode, it must be one of the codes from these codes).
* `cld.EXTERNAL_LANGUAGES`: list of external languages and their
codes. Note that external languages cannot be hinted, but may be
matched if you pass includeExtendedLanguages=True (the default).
* `cld.DETECTED_LANGUAGES`: list of all detectable languages, as best
I can determine (this was reverse engineered from a unit test, ie
it contains a language X if that language was tested and passes
for at least one example text).