Serious question. Which is easier on the eyes (less straining for long periods of time).

Black text on white background. OR
White text on black background?

@Ian_Fry
For me white text, black background.
@Ian_Fry
Gray text on dark blue, WordPerfect style.
@Ian_Fry I'm pretty sure I've seen scientists claim white text on black is less strenuous, but don't take my word for it.
Even better: Black or dark text on light grey/beige. Too much contrast can be tough too, I've heard.
@zatnosk I'm not sure what studies say, but I find light text on dark backgrounds hard to read. Grayish colors are even worse. I've been known to highlight the text on a page, then paste into a text editor so I can read light-gray on dark-gray or the reverse.
@lnxw48a1 in Firefox you can also try:
view → page style → no style
to see the text without weird colours (also without formatting)
@lnxw48a1 Obviously, there's also too little contrast, and it's very easy to stray into that. But pure black on pure white isn't the best option either, IMO :)
@Ian_Fry In low light, I prefer white on black. In abundant light, I prefer black on white.
@Flumberbug I think you have it nailed. Mastodon by default is white on black and I am finding it much easier on the eyes in the evenings than Tweetdeck is.
@Ian_Fry There is a "dark theme" Stylish style for twitter, don't know if it will work for Tweet deck. I always prefer night mode, and on top of that I use flux. For reading a book on a tablet I actually prefer light yellow/vanilla on black.

@TheRealMe Ah, I might have to look into that. Thanks.

Yeah, I have flux installed on my desktop. Lifechanger.

@Ian_Fry This is the one I use for twitter:

https://userstyles.org/styles/128569/twitter-dark-n-simple

If you open the editor you could try to add/change the domain in row 4. I am no expert, but that's how I got the mastodon flex width plugin to work for the instance I am on.

@Ian_Fry I think it's mostly about the dominant colour (the background) being a similar shade/brightness to your environment. That makes the text stand out a bit more.
People usually say black on white, but I find it quite stressing and do the opposite. Maybe it depends on the person.
@drymer I think white on black tends to be better in low light but it normal lighting conditions I don't know if there is a favourable one over the other.
@Ian_Fry black on an off white color
@Ian_Fry depends on how light it is in the room I suppose
@Ian_Fry personally, I find white text on black background easier to read. It's not a professional answer, just my impression.
@Ian_Fry For me, I prefer white text on black background. Others will say the opposite.
@Aine @Ian_Fry White text on black background for me.

@Ian_Fry It depends on the medium. Backlit devices, often times it's light on dark. Most other application, it's dark on light.

That being said, the reason most web material is dark on light is because it's what people were used to reading. Now we know better, but the decision appears to have already been made. Personally, my older eyes hate going from light-on-dark to the reverse. It's painful. Going from dark-on-light to the reverse is fine.

@Ian_Fry For me; it's a grey background with black text.