Why is Dark Mode not the default for websites/apps?

[AmbrusFernas]

I'm using Windows 10 on my desktop and MacOS Catalina on my MacBook. Dark mode within the OS (file explorer, Finder, etc.) is amazing, and so easy on the eyes. I'm wondering why it's taken 20-30+ years before they implemented this? Dark themes have been prevalent in the various Linux WM's/DE's for years, but never caught on in the "mainstream". I used to use a high contrast black theme on Windows XP to accomplish the same effect, but a native dark mode is just so relaxing.

There is even a blacked-out version of Google called Blackle, that touts how many KW-H of energy are saved from using a black background (to my understanding, black turns OFF the pixels, whereas white is all pixels ON at full-strength, therefore consuming more energy).

[ashiekh]

No energy saved as the lights work just as hard (the pixels let through or block light)

Now it is possible dark mode has one turning the brightness up, in which case it would actually waste energy.

[Polaris20]

Guess you missed the board for the post.

Black does NOT turns off the pixel in LCD - they are just 'blocked' by crystals. But in OLED - they do, because each pixel can be individually turned on and off.
The backlight is always turned on in LCD monitors(I mean the most case without local dimming feature), and the voltage on-off per each pixel(liquid crystal) varies by its panel type.
If your LCD is TN or IPS, max voltage is applied when it's black. In contrast, VA panel consumes least when it's white.
But the power consumption from liquid crystal is relatively small when compared to backlight, so it does not make practical differences in RL.

[GDILord]

Dark mode within the OS (file explorer, Finder, etc.) is amazing, and so easy on the eyes.

Because people are different. For me, it's not. Same with Office themes and Visual Studio themes. The younger kids at work like the dark themes, the rest of us don't and find it disorientating and difficult to use.

[ashiekh]

The old days of text terminals were dark background.

[GDILord]

Yep, that's how I grew up. GUIs changed that.

[vvvpcf]

I'd tested on my 23" IPS monitors.

[ashiekh]

A slight difference between black wallpaper and white, but certainly noticeable (1 W); thanks for taking the time to collect this data.

The question now is what brightness does an average user select for white mode vs dark mode.

[ehume]

Two things: data beats theory every time; this is the PSU board.

[ashiekh]

Data does not go far without theory (and vice versa)