April 15th, 2021
There is a lot to think about when implementing a dark mode theme on a website. We have a huge guide on it. There are some very clever quick wins out there, but there are also some quite tricky things to pull off. One of those tricky things is how it’s not a dark mode “toggle” between dark and light, but really three modes you need to support: dark, light, and use system preference. That’s similar to how audio preferences work in many apps, which allow you to very specifically choose which audio input or output you want, or default to the system preference.
prefers-color-scheme API, but if the user preference has changed, and that preference is now different than the user preference, you’re in the territory of “Flash of inAccurate coloR Theme” or FART. Ok ok, it’s a tounge-in-cheek acronym, but it’s potentially quite a visually obnoxious problem so I’m keeping it. It’s in the same vein that FOUT (Flash of Unstyled Text) is for font loading.
Storing a user preference means something like a cookie,
You can access a cookie with a server-side language before page-render, meaning you could use it to output something like
<html class="user-setting-dark-mode"> and style accordingly, which deftly avoids FART, but that means a site that even has access to a server-side language (Jamstack sites do not, for example).
Allllll that to say that I appreciated Rob Morieson’s article about dark mode because it didn’t punt on this important issue. It’s very specifically about doing this in Next.js, and uses
I’m not convinced there is a good way to avoid FART without a server-side language or force-delayed page renders.
The original post Flash of inAccurate coloR Theme (FART).