xkcd Hid a Spelling Joke in Their Website and It Quietly Changes the Header
Most people read xkcd for the comics. The devoted among you hover over every panel to catch the mouseover text. But there's a third layer hiding in plain sight, and it lives in a dropdown menu most readers walk right past.
The Mode Menu Nobody Noticed
On April Fools' Day, xkcd added a "Mode" dropdown below their comics. The comic that launched it was number 3227, titled "Creation." Which is either a coincidence or extremely on purpose. Knowing xkcd: extremely on purpose.
The available modes: Darkest Mode, Greyscale Mode, and Dorian Greyscale Mode.
Darkest Mode turns the screen black. That's the feature. You wanted dark mode, you got it. All of it. Enjoy.
Dorian Greyscale Mode Is a Two-Word Pun and You Should Stop and Appreciate It
Dorian Gray is the Oscar Wilde character who stays young while a portrait ages horribly in his place. "Dorian Greyscale" swaps "Gray" for "Greyscale." A visual pun, hiding in a UI dropdown, that requires you to know 19th-century literature to catch.
That's not a feature. That's a secret handshake for word people.
The Spelling That Flips a Word
Here's where it gets genuinely good. The menu includes both "Grayscale Mode" (American spelling) and "Greyscale Mode" (British spelling). One letter different. Same grey, different history.
Switch from Grayscale to Greyscale and something changes in the page header. "MATH" becomes "MATHS."
The website detects which spelling convention you chose and adjusts its vocabulary accordingly. One letter in the mode name shifts the entire linguistic register of the page. American gray gets American math. British grey gets British maths.
That is not a bug. That is a love letter to orthography.
The Overton Window in the Hover Text
The April 9, 2026 comic tucked a reference to the Overton Window into its mouseover text. The Overton Window describes the range of ideas considered acceptable in public discourse at any given moment. xkcd put the reference somewhere most readers never look.
One possibility is that hiding a concept about invisible limits inside an invisible layer of the page is the actual joke. Another possibility is it's just a mouseover. With xkcd, you can rarely rule out "both."
Easter Eggs That Only Work If You Know the Words
The Dorian Greyscale pun requires Wilde. The gray/grey toggle requires knowing those are regional variants of the same word. The Overton Window reference requires knowing what it means.
xkcd built a whole vocabulary into their interface and left it there for whoever showed up knowing the right words. That's the best kind of Easter egg. Not hidden behind a code. Hidden behind caring about language.
You're already the kind of person who reads articles about word nerdery on a puzzle website. You would have caught all three.
Source: Languagelog