1 · Carrier image
Drop a PNG here, or click to choose
Any image works — it's re-saved as lossless PNG so the hidden bits survive
2 · Secret
Load an image to see capacity.
3 · Result
The stego-image appears here once you embed a message.
Tip: download it, then load it into the Reveal tab to prove the message round-trips.
Stego-image
Drop the encoded PNG, or click to choose
Must be the lossless PNG — JPEG re-compression destroys the hidden bits
Recovered payload
Load an image and hit extract.
✓ Hidden message
How LSB works
Every pixel is three bytes — red, green, blue — each 0–255. Changing the lowest bit shifts a value by at most 1 (e.g. 200 → 201), invisible to the eye. We stream your message bit-by-bit into those low bits: a 12-megapixel photo hides ~4.5 MB of text with no visible change.
The header
The first bytes store a magic marker (NB) plus a 32-bit length, so the decoder knows exactly how many bits to read and can tell "no message" from garbage. It's the same trick CTF forensics challenges use — pair this with the CTF cheatsheet.