About

Synesthesia is when one sense reliably sets off another: a sound has a shape, a word has a taste, a month has a place in the room. The most common kind involving numbers and letters is called grapheme–color synesthesia — for the people who have it, a 7 simply is a color, the same one every time, with no effort and no choosing.

Estimates put synesthesia of some form in a few percent of people. If you have it, this site will feel obvious and slightly annoying: of course 3 is that color. If you do not, you can still play — most people who are asked to color the digits do not answer at random, and the crowd lands on patterns that are hard to explain away.

How this works

• You give each digit from 0 to 9 a color. One number at a time, in a random order.
• Your palette is kept in a single cookie on your own browser. No account, no email, nothing sent anywhere.
• Sharing puts the whole palette in the link, so the page and its social image are made from the URL alone. The server keeps no record of anyone's colors - not yours, not anybody else's.

Not a test

This is a toy, not a diagnostic. Real synesthesia research checks consistency: you are asked the same question weeks apart, and a synesthete gives nearly the same color every time. One sitting on a website cannot tell you anything about your own wiring.

Colophon

Server-rendered HTML with no framework, plain CSS, a sprinkle of JavaScript for the parts that want it, and a share image drawn pixel by pixel at the edge. It all runs in one Cloudflare Worker.