Petite caps

Petite caps are capital letterforms drawn to the x-height of the face they belong to, not merely shrunk to it. The stems are redrawn at the weight the lowercase around them carries and the letters are widened a little to survive the loss of height, exactly as small caps are, so the result reads as type rather than as a photographic reduction. What makes them petite is the target height: the flat top of a petite A lands on the same line as the top of an x.

That single number is the whole difference from small caps, and it changes what each is for. A small cap is drawn slightly taller than x-height, commonly five to fifteen percent, because it has to hold its own beside full cap-height letters: a small-caps heading or a run of small caps set as its own line of text. Petite caps have the opposite job. Set an acronym in small caps inside a paragraph and it still reads as a slightly raised, slightly louder run. Set it in petite caps and it stops announcing itself, because nothing in the line is taller than anything else. That is why the feature exists at all, and why it is most useful for abbreviations, units, and currency codes buried in running text.

The CSS is font-variant-caps: petite-caps, with all-petite-caps for text that is already uppercase, and the underlying OpenType tags are pcap and c2pc. The catch is supply. Almost no font ships a real petite-caps set, including the faces this site loads and every widely installed system face, and the specified fallback when pcap is missing is small caps: a browser substitutes the small-caps set, or synthesises one by scaling the capitals, and reports nothing. Two stylesheets asking for different things then render identically, which is the same silent failure every OpenType feature request carries.

So treat petite caps as a decision about a specific typeface rather than a property of text. Check the family’s own feature list first, and if pcap is absent, either use small caps and accept the slight lift, or set the height yourself: capitals at a reduced font size, tracked out a touch, with the size chosen so the cap height matches the x-height of the surrounding line. The specimen above does exactly that for its third sample, because no browser here honours the real request, and the caption says so.