Image Steganography

What it's for

Hide a message or a small file inside a picture so that the picture looks unchanged, then get it back out. The message is stored in the lowest bit of each pixel’s red, green and blue, which changes each colour by at most one step in 256.

For example, when you’re setting a puzzle and want the next clue hidden in a photo, or want to pass on a note that doesn’t look like a secret at all.

How to use it

You can drop files onto each of the three file boxes as well as choosing them. Under Hide, choose a cover image (JPEG, PNG, WebP or anything else the browser opens): its room for hidden data is shown. Type a message or choose a file, add a password if you like, and choose Hide in image. You get a PNG to download. With a password, the message is encrypted with AES-256 before it’s hidden.

Under Reveal, choose the PNG; any hidden message appears in the box, or a hidden file is offered to download. If it has a password, type it first, or type it and choose Reveal again.

Example

Choose any photo as the cover image, type this as the message and choose Hide in image:

The eagle lands at dawn.

Download the PNG, choose it under Reveal, and Found a hidden message. appears with the text. Add the password s3cret when hiding and the message can’t be read until you type it under Reveal.

Good to know

The result must stay a PNG, sent as a file. Anything that re-saves or converts the picture, such as most social networks and messaging apps, or exporting it as a JPEG, destroys the message. Room is about 3 bytes for every 8 pixels, so a 12-megapixel photo holds about 4.5 MB. Hiding is not encryption: anyone with this tool can find an unprotected message, so use a password for anything private. The hidden bits can be detected by statistical analysis, so this hides from people, not from forensics.