Free · No signup · Private
Invisible Watermark
Hide a secret text message inside a PNG image using steganography. The watermark is invisible to the human eye but can be extracted with our detector tool.
Note: Invisible watermarks are fragile — they are destroyed by resizing, cropping, JPEG compression, or screenshots. Output is always PNG.
Drop a PNG image here or click to upload
PNG files only
How to Use
1
Upload a PNG image
2
Type the text message you want to hide
3
Check that your message fits within the image capacity
4
Click encode to download the watermarked PNG
5
Use the Watermark Detector to verify the hidden message
Frequently Asked Questions
What is an invisible watermark?
An invisible watermark hides a text message inside the image data without visually altering the image. It uses LSB (Least Significant Bit) steganography to encode the message in the color channels of each pixel.
How does LSB steganography work?
Each pixel in an image has red, green, and blue color values (0-255). LSB steganography changes the last bit of each value, which is imperceptible to the human eye but encodes binary data. For example, changing a value from 200 to 201 is invisible but encodes a '1' bit.
Why does the output have to be PNG?
PNG uses lossless compression, which preserves every pixel value exactly. Lossy formats like JPEG alter pixel values during compression, which destroys the hidden message. The output is always PNG regardless of the input format.
What can destroy an invisible watermark?
Any operation that modifies pixel values will destroy the hidden message. This includes resizing, cropping, JPEG compression, taking screenshots, applying filters, color adjustments, or converting to a lossy format.
How much text can I hide in an image?
The capacity depends on the image dimensions. Each pixel provides 3 bits (one per color channel), so a 1000x1000 image can store about 375,000 characters. The tool shows the maximum capacity for your specific image.
Is my image uploaded to a server?
No. All encoding happens directly in your browser using the Canvas API. Your image and hidden message never leave your device.
How do I verify the watermark was embedded?
Download the watermarked PNG, then use our Watermark Detector tool to upload it and extract the hidden message. If the message is recovered correctly, the watermark is verified.
Can someone detect that my image has a hidden watermark?
LSB steganography is difficult to detect visually but can be found through statistical analysis tools. It provides a basic level of concealment suitable for proof of ownership, not military-grade secrecy.
Is this tool free?
Yes, the invisible watermark tool is completely free with no limits. No account or signup is required.
What are common uses for invisible watermarks?
Common uses include proving photo ownership, tracking unauthorized distribution, embedding copyright notices, adding metadata without visual clutter, and educational demonstrations of steganography.