Japanese dictionary data: JMdict, copyright the Electronic Dictionary Research and Development Group (EDRDG).
Source: https://www.edrdg.org/jmdict/j_jmdict.html
License: Creative Commons Attribution-ShareAlike 4.0 https://creativecommons.org/licenses/by-sa/4.0/
License statement: https://www.edrdg.org/edrdg/licence.html
JSON source: https://github.com/scriptin/jmdict-simplified (3.6.2, 2026-09-21 English release).
Changes: compacted to arrays of written forms, reading, English senses and common flag; sorted common entries first. The derived dictionary remains CC BY-SA 4.0.
Word frequency ranks: wordfreq 3.1.1 by Robyn Speer, https://github.com/rspeer/wordfreq
License: Creative Commons Attribution-ShareAlike 4.0. its Japanese list combines subtitles, Wikipedia, web text, Twitter and Reddit; see its README for the full source credits.
Changes: surface tokens folded into kuromoji dictionary forms and ranked (frequency.json, top 50,000). The derived list remains CC BY-SA 4.0.
Tokenizer: kuromoji.js by Takuya Asano, Apache 2.0. See KUROMOJI-LICENSE.txt and IPADIC-NOTICE.md in this directory.
JLPT levels: Jonathan Waller's JLPT Resources, http://www.tanos.co.uk/jlpt/ (Creative Commons BY), as linked to JMdict and respelled by https://github.com/stephenmk/yomitan-jlpt-vocab (original_data/n1–n5.csv).
There is no official JLPT vocabulary list; these levels are an informed estimate.
Changes: matched to this dictionary's entries by written form and reading (jlpt.json, "<word>|<reading>": 5 for N5 … 1 for N1); a word on two lists keeps the easier level.
Example sentences: the Tatoeba corpus (https://tatoeba.org), Creative Commons Attribution 2.0 France (CC BY 2.0 FR) https://creativecommons.org/licenses/by/2.0/fr/, as linked to JMdict senses in jmdict-simplified's "jmdict-examples-eng" 3.6.2 release.
Changes: Japanese/English sentence pairs deduplicated into examples.json ([Japanese, English, word as written, Tatoeba sentence id]); JMdict entries point to them by index.
Similar words: JMdict's own cross-references ("see also") and antonyms, kept in jmdict.json, plus common words whose English glosses match, computed in the browser.