Lining figures

Lining figures are numerals drawn on one line: every digit starts at the baseline and stops at roughly the cap height, so a row of them makes an even band with no digit poking up or hanging down. They are the default in almost every typeface released since the nineteenth century, which is why most people have never thought about the alternative. Set beside capitals they match, which is exactly what a date in a heading, a version number in a badge, or a figure in a table of interface chrome wants.

The alternative is oldstyle figures, where the digits take three different heights: some sit at the x-height, some rise to the ascender, and some hang below the baseline like lowercase descenders. Those belong in running prose, where a number set at cap height reads as a small shout in the middle of a sentence. The rule of thumb is simple: lining where the neighbours are capitals, oldstyle where the neighbours are lowercase.

It helps to see the two figure decisions as a grid rather than a list, because they are independent. Height is lining against oldstyle. Width is tabular against proportional: tabular gives every digit the same advance so columns line up down the page, proportional lets each digit take the width its drawing wants. All four combinations exist and are separately selectable, so tabular lining is the one for a table of amounts, proportional oldstyle the one for a paragraph, and the other two corners have their uses too. In CSS they are two independent keywords on font-variant-numeric, one from each axis, and in OpenType they are the four features lnum, onum, tnum and pnum.

The catch, as ever with OpenType, is that asking is not the same as receiving. font-variant-numeric: lining-nums does nothing unless the loaded face carries an lnum set, and a face whose defaults are already lining has nothing to switch to. Georgia is the useful counter-example: its default figures are oldstyle, so it is one of the few widely installed faces where turning lining figures on visibly changes the page. When the setting appears to do nothing, the font is the thing to check before the stylesheet.