How to Hide a Message in an Image (Steganography, Free + In-Browser)
Steganography hides a short text message inside the pixels of an ordinary image, so the picture looks unchanged but secretly carries your note. This guide shows how to hide a message in a PNG and read it back later, optionally locked with a password - all in your browser, so the image and the message never leave your device.
Last reviewed: 2026-06-16
| Property | Value |
|---|---|
| Format | Online, no install, no sign-up |
| Cost | Free |
| Implementing tool | https://freetoolonline.com/image-tools/steganography.html |
How to hide a message in an image
- Open the Steganography tool and keep the mode on "Hide a message in an image".
- Choose a cover image. A PNG works best; a larger image holds a longer message.
- Type the secret message you want to hide. The tool shows the most characters that image can hold before you embed.
- If you want, add a password so only someone who knows it can read the message back.
- Click the hide button and download the result. Keep it as a PNG.
How to read a hidden message back
- Open the same tool and switch the mode to "Reveal a hidden message".
- Choose the PNG that was made with this tool.
- If the message was locked, enter the password. The hidden text appears on the page.
Why the result has to stay a PNG
The message is stored in the least-significant bit of each pixel - a tiny change the eye cannot see. PNG is lossless, so those bits survive. If you re-save the image as JPG, or run it through a compressor, the bits are rewritten and the hidden message is erased. Most social and messaging apps also re-compress images, so send the PNG as a file rather than a photo if you need the message to survive.
How much text an image can hold
Each pixel stores three bits (one in red, green, and blue), and every character uses sixteen bits, so capacity grows with the pixel count. Rough guide:
| Image size | Pixels | Approx. characters |
|---|---|---|
| 64 x 64 | 4096 | about 762 |
| 256 x 256 | 65536 | about 12282 |
| 512 x 512 | 262144 | about 49146 |
If a message is too long for the chosen image, the tool tells you the maximum and stops rather than cutting the text off silently.
Is it private?
Yes. Everything runs in your browser on your own device; the image and the message are never uploaded to a server. Note that steganography hides the existence of a message from a casual viewer, but a determined analyst running statistical checks may still detect that data is present, so treat the optional password as the real protection for the contents.