Every serious reading medium — books, newspapers, documents, most of the web — settled on dark text over a light background. That was not habit; it is how human vision prefers to read.
The optics of dark-on-light
A bright background constricts the pupil. A constricted pupil acts like a smaller camera aperture: greater depth of field, sharper focus, and less impact from small imperfections in the eye’s lens. Dark letterforms on that bright field hold their edges — no halation, no bloom. This is the mirror image of what happens with white text on black, where the dilated pupil works against you.
The numbers
Pure black #000000 on pure white #FFFFFF measures 21:1 — identical to its inverse, but without the glow penalty. In practice many designers soften it: #16181D or #212121 text on white lands around 16–18:1 and feels less stark on large bright monitors, while off-white backgrounds (see off-white shades) around #FAF9F6 reduce glare in bright rooms at almost no contrast cost.
When to soften, when not to
Soften for long-form reading on large screens. Keep maximum contrast for small text, low-quality displays, outdoor/bright-sunlight use, and any accessibility-first context — reduced contrast disproportionately hurts low-vision readers. The common “grey text everywhere” aesthetic is a different problem entirely — we covered its failure modes in grey text on white.
Test any color pair yourself with our free contrast checker — live WCAG ratios as you pick.