The logic of #000000 is wrong from the start
The instinct makes sense: dark mode means dark, so go darkest. A background of #000000 paired with white text produces the highest possible contrast ratio — around 21:1, the ceiling of the WCAG scale. It feels rigorous. It also makes reading harder.
The eye doesn't measure contrast mathematically; it adapts. On a predominantly black screen, white text becomes a light source. The phenomenon is well-documented in vision science: high-luminance text against a near-zero-luminance background causes halation, a blooming effect where letterforms appear to bleed at their edges. The word gets fuzzy. Reading slows. The very move that looked correct by the numbers degrades the experience those numbers are supposed to guarantee.
This is why almost every reading-optimised dark interface settles on a background somewhere between #121212 and #1e1e1e — a grey dark enough to read as black, light enough that white text stays text rather than glare. The perceptual difference from pure black is dramatic; the measured difference is negligible.
Then there is the OLED problem, which is different in kind. Organic light-emitting diode panels produce black by switching pixels off entirely. This is why OLED black is genuinely black — it emits no light at all — and it is why those screens are sold partly on contrast. But when content moves across an off-to-on boundary, the transition speed of OLED pixels is not uniform across the luminance range. Very bright pixels turning on against very dark surroundings can trail — a smearing or ghosting artefact that is invisible on LCD and real on OLED. Fast-scrolling white type on a pure black background is close to the worst case: maximum delta, maximum speed, maximum visibility of the artefact.
Raising the background from #000000 to something in the #111–#1a1a1a range reduces that luminance cliff without meaningfully lifting ambient brightness. The pixels that were off are now dim; the transition is softer; the smear disappears. The dark theme as a second palette argument applies here too: dark mode deserves its own considered choices, not inverted defaults or maximised values.
Pure black works in one place: behind full-screen video or imagery, where it functions as a true surround rather than a reading surface. Everywhere else it is a number that feels like a decision but isn't one.