What Is Leading (Line Spacing)?
Leading (rhymes with "heading") is the vertical space between lines of text, measured baseline to baseline. The term comes from strips of lead inserted between lines of metal type. Generous leading makes paragraphs easier to read; too little crowds the lines and the eye loses its place.
In CSS, leading is controlled by `line-height`. A common starting point for body text is a line-height of about 1.4–1.6 times the font size.
Optimal leading depends on line length and font size: longer lines and larger x-heights generally need more leading to stay comfortable.