What to do

Implement Dark mode as a Beta preference. When users select the global or local Beta preference, the system will put the dark mode on/off switch (T221897) on every page of the specified Wikipedia(s), enabling the user to turn Dark Mode on and off.

Local vs. Global beta

This feature will be available only on desktop Wikipedias in its first implementation. So it will show up as a local Preference only on Wikipedias. However, it can still be a Global preference (Roan confirms that you can have a "Global" preference that is limited to some subset of wikis.)

Elements and text for beta listing

• Beta feature title: Dark mode
• Descriptive text: A new reading mode that's easier on the eyes in low light. Selecting this feature adds a switch to the top of every page, enabling you to turn Dark mode on and off (currently on desktop Wikipedias only).
• "Information" link: goes to the project page.
• "Discussion" link: goes to the project talk page.
• Dark mode icon: TO COME FROM @alexhollender