The problem

Dark mode is often sold as an energy feature. On OLED phones it helps at full brightness, but at the 30-50% brightness most people use indoors the saving is small.

The fix you can use today

• Offer dark mode (users like it) but don't claim big energy savings for it.
• Spend your effort on bytes, JavaScript and background work first.
• If you make energy claims, measure on real devices at real brightness.

Researchers at Purdue University found that dark mode saves little battery at normal screen brightness. GreenCode keeps advice like this in mind in its work.

Tools that help

• Lighthouse: audits a page for total byte weight, unused JavaScript and CSS, image formats and offscreen images

How GreenCode helps

GreenCode helps tackle this by cutting page weight on its own website: static pages, WebP images, scripts only where they are used and purged styles took the home page's first view from 6,766 KB to 1,719 KB. More on this.

Tags

#mobile#ux#devices

Sources

• Purdue University news, Dark mode may not save your phone's battery life as much as you think (2021)
• Dash and Hu, How much battery does dark mode save? (MobiSys 2021)
• W3C, Web Sustainability Guidelines: prefers-color-scheme and preference media queries

All GreenCode Tech Tips