The default background colors on early browsers wasn't always white. On Netscape Navigator on the Mac up to about version 4 the default background color was #C0C0C0 (IIRC). I seem to recall that also being Mosaic's default background color. Navigator on Windows had white as the default background color as did IE.

My first excursions on the web were on Macs so I thought something pages were doing some Windows-specific trickery when I first saw the same pages on Windows with white instead of grey backgrounds.

Even a lot of books on HTML in the early days had screenshots from Macs and you'd follow an example on Windows and the output would look different because of the different default background color.

The industry has cycled back and forth between "dark mode" and "light mode" several times. Browsers first appeared in a "light mode" era, which I suppose probably began with the Lisa then the Mac, then Sun workstations. Black-on-white needed a more expensive high performance CRT and graphics output circuitry so possibly there was an element of chic associated with it vs lowly green/white text terminals that came before.

Yep. I think by the time the web arrived, it was pretty common for the windowing systems (e.g., Windows, Mac System whatever, OpenVue, Next, etc.) to have black text on white backgrounds to mimic paper output.

To match word processors in looking like paper maybe?

many of the suggestions are part of the right set of ideas, there was more than one reason, including mimicking paper. at that time many of these things were new and hadn't been done before, so they were done to show that it could be done or to see how it looked and it was fresh. (like the iphone's new liquid glass, is that really the best idea for a UI (feels it was only yesterday we got rid of the <blink> tag) or is it just new?)

so to add to the mix, that with a monochrome display, relatively low rez lighted pixels making letters (on a black background) still has the letters looking pixelated. the same lighted pixels making a white background leaves the black letters looking smoother.

outside of "labs", i remember the VT-100 being the first "white paper" display that was generally in use, but that could have been a regional thing in the shadow of the Maynard mill.

More or less, from what I've read. Once there wasn't a technical issue, a white (or near white) background became seen as more user-friendly than a black background.

Or you could opt for WordPerfect's compromise: white-on-blue.

I'll still use that as an editing background at times.