🪡Hiding a sentence in plain sight

This website is hiding something. The footer has been telling you since the day it launched. This post explains the trick — though not the secret itself.

Where it started

My first real projects, back in university, were steganography tools: iSteg hid text inside images, aSteg hid files inside audio. The appeal was never the cryptography — it was the idea that a thing could look completely ordinary and still carry a payload.

Two ways to hide text in a webpage

In an image: least significant bits

Every pixel in a PNG has red, green and blue channels, each a number from 0 to 255. Flip the lowest bit of any of them — turn a 142 into a 143 — and no human eye can tell the difference. Do that systematically and an image becomes a container:

message bit:   1        0        1        1
red channel:   10001110 → 10001111
green channel: 01101001 → 01101000
blue channel:  11010100 → 11010101

A 1000×800 photo gives you 2.4 million channels — nearly 300 KB of hidden capacity in an image that looks untouched. That’s what iSteg did in 2018, and it’s what the /steg page on this site does today, entirely in your browser.

In text: zero-width characters

Unicode contains characters with no visual width at all — the zero-width space (U+200B) and the zero-width non-joiner (U+200C). Sandwich them between normal letters and the text looks identical, but the character stream now carries extra data: treat one as binary 0, the other as 1, and any sentence becomes a covert channel.

This very site uses that trick. Somewhere on the homepage, a perfectly normal looking sentence says more than it appears to.

Finding it

The /steg page has a decoder. What you paste into it is up to you.

Happy hunting.