Baseline (typography)

A baseline is an imaginary line along the inline axis of a line box along which individual glyphs of text are aligned. Baselines guide the design of glyphs in a font and the alignment of glyphs from different fonts or font sizes when typesetting.

The alphabetic baseline is the value of the CSS baseline keyword. The bottom of most alphabetic glyphs typically align with the alphabetic baseline; most characters of European and West Asian fonts rest on top of the alphabetic baseline.

Other writing systems have different baselines. For example, Tibetan and similar unicameral scripts with a strong but not absolute top edge are aligned to the bottom of a "hanging" baseline. East Asian scripts have no baseline; each glyph sits in a square box, with neither ascenders nor descenders. When mixed with scripts with a low baseline, East Asian characters should be set so that the bottom of the character is between the baseline and the descender height.