The deck is built from public Japanese government language data and a small
number of other sources. Each is listed below with the terms it is used
under. Where attribution is a condition of use, this page is where it is given.
Kanji frequency and level ordering
「漢字出現頻度数調査（４）」文化庁国語課（令和４年２月）
Kanji Frequency Survey (4), Agency for Cultural Affairs, National Language Division, February 2022
Every character's rank, and therefore which level it lands in, comes from
this survey. It counts roughly 51 million kanji across dictionaries,
books, weekly and monthly magazines, and textbooks published between
2018 and 2020.
A 調査報告 (research report) rather than a 告示, so it is used under the
Agency for Cultural Affairs' site terms, which permit commercial use and
are declared compatible with CC BY 4.0. Attribution is required.
The kanji set
常用漢字表（平成22年内閣告示第2号）
List of Kanji for General Use, Cabinet Notification No. 2 of 2010
The backbone of the deck. Kanji Drift teaches more than this list —
the jōyō boundary is a policy decision rather than a frequency one, and it
leaves out characters you meet in ordinary writing — but every character
in it is here.
Cabinet notifications are exempt from copyright under Article 13(ii) of
the Japanese Copyright Act. No licence or attribution is required; it is
credited here because it should be.
School grade assignments
学年別漢字配当表（文部科学省告示）
Kanji by School Year, Ministry of Education notification
Which school year a character is taught in, where that is shown.
Also a 告示 — exempt under Article 13(ii).
Radicals and character structure
The Unihan Database, Unicode Consortium
The classical 214 Kangxi radical index for every character, plus stroke
counts and readings for characters outside the jōyō set.
Used under the Unicode Terms of Use, which permit commercial use.
JLPT vocabulary and kanji lists
Jonathan Waller's JLPT resources
The N5–N1 vocabulary and kanji lists behind the exam-oriented study paths.
No official JLPT list has been published since 2010, so every N-level
assignment in circulation is an editorial reconstruction; this is a
well-regarded one.
Used with the author's permission.