Slabo 13px
Google Fonts · John Hudson · 2013

A serif typeface designed with singular purpose: to render cleanly and legibly at exactly 13 pixels on screen.
About
Slabo 13px is an unusual specialism in type design — a face built entirely around a single pixel size rather than broad optical flexibility. Designed by John Hudson of Tiro Typeworks, it excels in small UI text, footnotes, and interface labels where screen rendering at 13px is fixed. It is not intended for print or large display settings.
Classification
Slabo 13px is a serif typeface engineered specifically for rendering at 13 pixels on screen, with carefully tuned proportions and spacing to ensure legibility at that precise size. Its design sacrifices conventional optical harmony in favour of pixel-perfect clarity.