Image Steganography
Hide a secret message inside a picture that looks exactly the same.
How to use the Image Steganography
- Choose Hide a message, then drop a picture.
- Type your message and, ideally, a password.
- Download the new PNG. It looks the same as the original.
- To read it, choose Reveal a message, drop that PNG and enter the password.
About this tool
Steganography is the art of hiding a message in plain sight. This tool tucks your text into the tiniest detail of a picture: the last bit of each pixel's red, green and blue values. Changing that bit alters a colour by one step out of 256, far too little for anyone to see, so the picture looks identical while carrying your message.
Hiding is not the same as locking. Anyone who suspects a message and uses a similar tool can pull it out, so add a password: the message is then encrypted with AES-256 before it is hidden, and without the password the extracted data is meaningless. A wrong password, or a picture that has been altered, is reported clearly.
The hidden bits are fragile by design. Saving as JPG, resizing, editing, taking a screenshot or sending the picture through apps that recompress images all destroy the message. Share the PNG as a file, for example by email attachment or a file-sharing link. A picture of one megapixel can hold over 300,000 characters.
Frequently asked questions
Can people tell a picture has a hidden message?
Not by looking. Statistical analysis can sometimes detect that the lowest bits were changed, so treat steganography as a way to avoid attention, and rely on the password for secrecy.
Why did my message disappear?
The picture was changed after it was saved: converted to JPG, resized, cropped, screenshotted or compressed by a messaging or social app. Always share the original PNG file.
How long can the message be?
About three bits per pixel. The tool shows the available space as you type; a typical phone photo can hold far more text than you are likely to need.
Do transparent pictures work?
Yes, but only fully opaque pixels are used, because browsers alter the colour of transparent pixels. A picture with large transparent areas holds less.
Is my picture or message uploaded?
No. The pixels are changed, and the message encrypted, inside your browser. Nothing is sent anywhere.