A font is the design data used to render characters on screen or in print. Strictly speaking, a "typeface" is the design concept (e.g., Helvetica) and a "font" is a specific implementation of that design (e.g., Helvetica Regular 16px), but today the two terms are largely synonymous. The choice of font directly influences text readability, visual impression, and the display width of characters.

Japanese fonts are broadly divided into Mincho (serif) and Gothic (sans-serif) families. Mincho features thin horizontal strokes and thick vertical strokes that evoke the feel of brush writing, making it the standard for book and newspaper body text. Gothic has uniform stroke widths and high visibility, making it well suited for headings and web body text. On the web, specifying font-family: "Noto Sans JP", sans-serif to use a Gothic typeface is common practice.

The relationship between fonts and character count differs significantly between proportional and monospaced fonts. In a proportional font, "W" and "i" have different widths, so the same number of characters can occupy different amounts of space. In a monospaced font, every character has the same width, allowing display width to be calculated precisely from the character count. In Japanese monospaced fonts, full-width characters are exactly twice the width of half-width characters.

The advent of web fonts has dramatically expanded the range of available typefaces. Google Fonts offers over 1,500 fonts for free, including Japanese options such as Noto Sans JP, Noto Serif JP, and M PLUS 1p. However, Japanese font files are large (1 to 5 MB due to the kanji they contain), which can affect page load speed. Subsetting (extracting only the characters actually used) and font-display: swap are important optimization techniques.

There are situations where font choice affects character count in practice. When fitting text into a physical space such as a business card or poster, the font determines how many characters will fit. A condensed (narrow) font allows more characters in the same space at the cost of readability, while a generous font fills the space with fewer characters.

From an accessibility standpoint, a font size of at least 16px and a line height of 1.5 or more are recommended. For users with dyslexia, fonts with wider letter spacing and clearly distinguishable similar-shaped letters (b/d, p/q) - such as OpenDyslexic - can be helpful. Font selection is a critical design decision that affects not only how character counts appear visually but also whether readers can comprehend the text. Font and design books on Amazon delve into these considerations.