Hide Text in an Image

How hiding text in an image actually works

This page hides plain text inside a photo by editing bits you can't see — here's exactly what happens to your file and how much you can fit.

Method

LSB (least-significant-bit) encoding — the lowest bit of each pixel's red, green and blue value is replaced with one bit of your message. The alpha (transparency) channel is left untouched.

Data rate

3 bits per pixel (one per RGB channel), so roughly 1 byte for every 3 pixels, minus a 9-byte header.

Visible change

At most ±1 on a 0–255 colour scale per channel — far below what the eye can perceive, so the picture looks identical.

Password option

Optional. With a password the message is encrypted before embedding using a key stretched from your password with AES-256-GCM + PBKDF2 (SHA-256, 600,000 iterations) plus a random salt; without one, the bits are hidden but not encrypted.

Output format

Always a lossless PNG. JPG and WebP re-compress the pixels, which would wipe out the hidden bits, so the tool never exports those.

How much fits

Capacity scales with pixel count. A 1280 × 720 image holds about 337 KB of text (roughly 346,000 plain ASCII characters); a small 600 × 400 photo still holds about 88 KB. The live meter in the tool shows the exact limit for the image you load, and non-Latin characters (which take more than one byte in UTF-8) use up the budget faster.

Security: it hides, it doesn't lock

Hiding is not the same as locking. Steganography hides that a message exists; it does not, on its own, scramble what the message says. Anyone who knows to run this kind of image through an LSB extractor can read an un-passworded message. For real secrecy, set a password so the text is encrypted as well as hidden — and remember that LSB is not designed to survive forensic statistical analysis.

Tips that actually matter

• Keep and share the exact PNG the tool produces. Screenshotting it, re-saving it as JPG, or letting a chat app auto-compress it re-encodes the pixels and erases the hidden message.
• A detailed, noisy photo is a better cover than a flat one: the tiny bit-level changes blend into existing texture instead of standing out in a large block of solid colour.
• Want it readable only by the right person? Add a password — the text is encrypted first, so even someone who suspects the image carries data can't read it without the key.