Most of the data that I've found suggests that dark text on a light background is measurably more legible than the reverse. This effect is increased for people with astigmatism -- which is about half the population, so that's not insignificant.

There's a lot of pushback I've seen when studies like that get cited: they're old, they weren't about programmers, etc. And, maybe, but even though we're staring at LCD panels now rather than CRTs, light is light light and vision is vision. It's not about how much light is "shining into your eyes" as much as it is about visual acuity, and it's at least worth trying light mode and just... turning down the brightness on your monitor a little. Also, turning up the ambient light in the room. If your environment is so dark that the backlighting on your keyboard is visible, then you've tacitly designed your environment to make light mode blinding and uncomfortable, so you're not really giving it a fair shake.

I'd like to see studies about whether alternating between dark and light mode occasionally will help prevent your eyes from getting tired as quickly; my suspicion is yes, because it certainly does feel that way to me. But a lot of things that seem intuitively true don't stand up to scrutiny.

I imagine you don't know the answer, but I'm curious as to if these studies were controlled for screen glare.

Dark themes/backgrounds have far worse issues with screen glare from badly configured room lighting than light ones do in my experience.

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I'm also curious why another area of design that is extremely concerned with legibility seems to have reached the opposite conclusion, pretty much worldwide.

Road signs.

Even though signs themselves can vary widely, the standard color scheme for road signs in every developed country I can think of, is a darker background with lighter text. I certainly don't have the studies in front of me, but I know a great deal of research has gone into fonts and legibility for road signs, and I presume what we see on the roads in the world is the result.

You are correct, I don't know if they controlled for screen glare. :)

The road signs are an interesting question. I know there's a lot of work, and occasional controversy, over the typefaces used. If I had to hazard a guess for the color choices, though, it might be the signs have to be very visible in the dark, too -- that's now generally done by using reflective paint for the light part of the sign, but older highway signs, at least in America, used reflective dots in the letters. So that might be a tradition born less out of legibility studies than practicality.

My astigmatism gives me doubles in any high contrast situation, whether light on dark or dark on light. Solarized/Zenburn type low-contrast palettes are the only thing that really addresses it.

I've noticed that when my eyes are tired as well. I think well-considered low-contrast color schemes don't get enough love, and I'm still a fan of Solarized, too. (Although my favorite schemes, both light and dark, are Spacemacs'.)

I would say you have an interesting article here, and your user poll is interesting too. But like you said you don't really have the data to back up this claim, so it just comes off as really click-baity. It worked, as I've never heard of your product and am clicking around the site now, but it's disappointing none the less.

I think it would be fine if the title just said "95% of our users prefer dark mode" rather than trying to generalize it to all people.