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About Kuromoji

Kuromoji is an open source Japanese morphological analyzer written in Java.

Kuromoji has been donated to the Apache Software Foundation and provides the Japanese language support in Apache Lucene and Apache Solr 3.6 and 4.0 releases, but it can also be used separately.


  • Download Apache Lucene or Apache Solr if you want to use Kuromoji with Lucene or Solr. See below for some usage details.
  • Download from GitHub if you would like to use Kuromoji for standalone applications.

About Atilika

We are a small R&D and consulting company based in Tokyo.

We are proficient in the fields of search, natural language processing, big data and more. Please see our homepage for more info.

Internship position We have an internship opening in Tokyo for a very passionate programmer. Read more

Contact us

Please feel free to contact us on kuromoji at atilika dot com if you have questions or feature requests. 日本語でも大丈夫です。

Kuromoji supports standard morphological analysis features such as

  • Word segmentation - segmenting text into words (morphemes)
  • Part-of-speech tagging - assign word-categories (nouns, verbs, particles, adjectives, etc.)
  • Lemmatization - get dictionary forms for inflected verbs and adjectives
  • Readings - extract readings for kanji

Try Kuromoji right here

Enter Japanese text below in UTF-8 and click Tokenize.

Tip This demo is also available separately on

Try Kuromoji from the command line

Try Kuromoji from the command line using the below commands, and then write some text followed by RET.

% java -cp kuromoji-0.7.7.jar org.atilika.kuromoji.TokenizerRunner
Tokenizer ready.
すもも	名詞,一般,*,*,*,*,すもも,スモモ,スモモ
も	助詞,係助詞,*,*,*,*,も,モ,モ
もも	名詞,一般,*,*,*,*,もも,モモ,モモ
も	助詞,係助詞,*,*,*,*,も,モ,モ
もも	名詞,一般,*,*,*,*,もも,モモ,モモ
の	助詞,連体化,*,*,*,*,の,ノ,ノ
うち	名詞,非自立,副詞可能,*,*,*,うち,ウチ,ウチ

Info You may need to add option -Dfile.encoding=UTF-8 to get a suitable output in your terminal, depending on your system.

Kuromoji provides the Japanese language support in the upcoming Apache Lucene and Apache Solr search products (3.6 and 4.0).

The Kuromoji integration in Lucene/Solr ships with a ready-to-use default configuration that does:

  • Light stopwords/stoptags removal - removes particles and common words to prevent rank-skew
  • Character width-normalization - full-width romaji to half-width and half-width kana to full-width
  • Lemmatization - reduces inflected adjectives and verbs to their base form

Additional to the above, there are lots of useful token attributes with readings, romanized readings, part-of-speech, etc. The above is available in Lucene as JapaneseAnalyzer and a default field "text_ja" in Solr's example schema.xml. Configuration options are of course also available.

Tip To search Japanese using Solr, simply use field type "text_ja".

Tip To search Japanese using Lucene, all the above is available using JapaneseAnalyzer.

Search mode and synonym compounds

In search mode, we want to split compounds in order to make their parts searchable, which is good for recall.

In order to make sure we maintain precision for an exact term match, we also keep the compound in our index as a synonym to get a rank boost (typically from IDF).

Kuromoji makes recall and precision considerations for overall good ranking.

Position 1 Position 2 Position 3
関西 国際 空港
Tokens for 関西国際空港. We keep the compound as a synonym in position 1.

Apache Solr 4.0 analysis screenshot

Below is an analysis screenshot of Solr 4.0 for the text 関西国際空港から出発した (I departed from Kansai International Airport).

Info Several token attributes available, including part-of-speech tags, readings, romanized readings, etc.

Kuromoji is packaged as a single jar file, is Mavenized (see below), and doesn't have 3rd party dependencies to make it easy to work with.

Below is a simple Java example that demonstrates how a simple text can be segmented.

package org.atilika.kuromoji.example;

import org.atilika.kuromoji.Token;
import org.atilika.kuromoji.Tokenizer;

public class TokenizerExample {
    public static void main(String[] args) {
        Tokenizer tokenizer = Tokenizer.builder().build();
        for (Token token : tokenizer.tokenize("寿司が食べたい。")) {
            System.out.println(token.getSurfaceForm() + "\t" + token.getAllFeatures());

Compile the example program using

% javac -encoding UTF-8 -cp lib/kuromoji-0.7.7.jar src/main/java/org/atilika/kuromoji/example/

and then run it using

% java -Dfile.encoding=UTF-8 -cp lib/kuromoji-0.7.7.jar:src/main/java org.atilika.kuromoji.example.KuromojiExample
寿司	名詞,一般,*,*,*,*,寿司,スシ,スシ
が	助詞,格助詞,一般,*,*,*,が,ガ,ガ
食べ	動詞,自立,*,*,一段,連用形,食べる,タベ,タベ
たい	助動詞,*,*,*,特殊・タイ,基本形,たい,タイ,タイ
。	記号,句点,*,*,*,*,。,。,。

Tip Kuromoji is thread-safe so you can tokenize text from multiple threads.

To use Kuromoji with Maven, first add the repository to the <repositories> section of your pom.xml as indicated below.

    <id>Atilika Open Source repository</id>

Then add the Kuromoji coordinates to the <dependencies> section as follows:


You should now be able to use Kuromoji in your project.

Various additional information about Kuromoji is provided below.


Kuromoji is licensed under the Apache License v2.0 and uses the MeCab-IPADIC dictionary/statistical model. See NOTICE.txt for license details.

Dictionary support

Kuromoji supports the MeCab-IPADIC dictionary and has experimental support for UniDic. Contact us if you need additional dictionary support.

Thread safety

Kuromoji is thread-safe.