WhatsApp dark is a simple dark style for WhatsApp Web.
Install Stylus for either Firefox, Chrome/Chromium/Brave/Vivaldi or Opera or Cascadea for Safari and then:
Install the usercss which supports automatic updates.
This is a mirror of my style WhatsApp Dark Theme by Prognoz hosted in userstyles.org. And this repository will now be the official place to distribute the style, since userstyles is basically dead.
Also, the CSS is a monstruosity but it works. WhatsApp Web thankfully started using CSS custom properties some time ago, but almost all the old code is still in in the CSS, so many rules are just old code, I'm to lazy to clean up that mess for the moment.