Not for the people who never use it. A reader who leaves the page light downloads about six kilobytes, compressed — a small script and a small stylesheet — plus about two kilobytes in the page itself that set the colours before the first paint. Page weight on the Dashboard shows the exact figure. The engine that does the re-colouring is about 39KB and is fetched whenever a page is shown dark — by the reader's choice, by their device setting, or by your schedule. It also makes Automatic the heaviest method on the reader's device: measured, about 155 ms of extra work per dark page on a desktop and about 475 ms on a mid-range phone.
If you pick Basic (no JavaScript) on the Colours screen there is no engine at all: the colours are written into the page and no JavaScript runs after it loads.
Still stuck? Ask the developers who wrote it. We aim to reply within one business day.
Dark Mode
Give your site a dark mode your readers can switch on — one that reads properly on every page, without you restyling anything.
From $19 a year · every feature · 30-day refund
