Line height refers to the vertical distance between lines of text. In CSS, it is controlled by the line-height property and can be specified as a multiplier (e.g., 1.5) or a fixed value (e.g., 24px).

Proper line height significantly affects text readability. For body text, a multiplier of 1.5 to 1.8 is generally recommended, while headings work well at 1.2 to 1.4. Typography fundamentals books teach the principles of line spacing design.

CJK text (Chinese, Japanese, Korean) typically requires wider line spacing than Latin text due to the larger character faces of kanji and kana.

Line height that is too tight makes text feel cramped and hard to read, while excessive spacing causes the eye to lose track of the next line. Web design and typography books provide practical guidelines for line-height settings.