How does zero-width steganography work?

Each character of the secret is converted to 8 bits. A bit value of 0 is stored as a zero-width space (U+200B) and a bit value of 1 as a zero-width joiner (U+200D). These characters take no visible space, so the cover text looks unchanged.

Why is the hidden text invisible?

Zero-width characters are real Unicode code points designed for typographic control, but they render with no width. Embedded among normal letters they are imperceptible to a reader while still surviving copy and paste.

No. It is concealment, not encryption. Anyone who knows the zero-width scheme can decode the payload, so encrypt the secret first if you need genuine confidentiality.

Where does the payload sit in the cover text?

This tool appends the zero-width sequence after the first character of the cover text so it is carried inside the string. Decoding scans the whole string for zero-width characters regardless of position.

Will the hidden message survive everywhere?

Often on platforms that preserve Unicode, such as chat apps, documents and many web forms. Some systems strip or normalise zero-width characters, which would erase the payload, so test your channel first.

Zero-Width Character Steganography

What this tool does

This is a zero-width steganography encoder and decoder. It hides a secret message inside invisible Unicode characters that occupy no visible space, so the cover text appears completely normal while secretly carrying your payload.

How it works

The encoder uses two zero-width code points as binary digits:

Zero-width space U+200B represents bit 0
Zero-width joiner U+200D represents bit 1

Each character of the secret is converted to its 8-bit value, every bit is mapped to one of those two invisible characters, and the sequence is embedded into the cover text. To keep the payload self-contained, the tool also frames it with a zero-width non-joiner U+200C boundary marker so the decoder knows exactly where the hidden data starts and ends.

Decoding scans the text for these zero-width characters, converts each back to a 0 or 1, regroups the bits into bytes, and reconstructs the original characters.

Example

The letter H is 01001000. Encoded, it becomes eight invisible characters — alternating zero-width spaces and joiners — that a reader never sees but the decoder turns straight back into H.

Notes

This is concealment, not encryption: anyone who knows the scheme can read it. Encrypt first if you need secrecy.
Some platforms normalise or strip zero-width characters; verify your delivery channel preserves them.
Because the payload is pure Unicode, it survives ordinary copy-paste better than trailing whitespace does.