The Joyo Kanji are the 2,136 characters listed in the Joyo Kanji Table, last revised in 2010. The table is defined as "a guideline for kanji usage when writing modern Japanese in general social contexts such as legislation, official documents, newspapers, magazines, and broadcasting." While not legally binding, newspapers and publishers use it as the primary reference for deciding which kanji to use and which to avoid.

The history of the Joyo Kanji Table dates back to the 1946 Toyo Kanji Table (1,850 characters), which had a restrictive character, strongly discouraging the use of kanji outside the list. In 1981, it was replaced by the Joyo Kanji Table (1,945 characters), which adopted a softer stance as a "guideline" rather than a restriction. The 2010 revision added 196 characters and removed 5, bringing the total to 2,136. Among the additions were visually complex but commonly used characters such as the kanji for "depression" and the kanji in the word for "vocabulary."

The Joyo Kanji list has a direct impact on character count in Japanese writing. Newspapers generally write within the Joyo Kanji set, adding furigana (ruby annotations) to non-Joyo kanji or replacing them with hiragana. Converting a single kanji to hiragana typically expands it to 2 to 4 characters (for example, the kanji for "rose" becomes four hiragana characters), so the scope of the Joyo Kanji list directly affects the length of a text.

In education, the Joyo Kanji are taught progressively over nine years of compulsory schooling (six years of elementary school and three years of middle school). The 1,026 kanji taught in elementary school are called "Education Kanji," with a fixed allocation per grade: 80 in first grade, rising to 191 in sixth grade. When designing content for children, the character set must be limited to the kanji the target age group has already learned. Kanji study materials on Amazon are organized by grade level for this reason.

In terms of computer character encoding, the JIS X 0208 Level 1 kanji set (2,965 characters) includes all Joyo Kanji. This means there is no Joyo Kanji that cannot be represented in Shift_JIS or EUC-JP. Unicode covers an even broader range, and every Joyo Kanji is located within the BMP (Basic Multilingual Plane).

For character counting in practice, knowledge of the Joyo Kanji is useful for designing readability metrics. Text with a high proportion of Joyo Kanji is easier for a general audience to read, while text heavy with non-Joyo kanji gives a specialized or difficult impression. Some text analysis tools calculate the Joyo Kanji usage rate to evaluate the difficulty level of a piece of writing.