Messages you cannot see

Unicode includes characters that take up no space at all, like the zero-width space. They are invisible on screen but still travel with the text when it is copied. Strung together, they can carry a whole message inside a sentence that looks completely normal. That makes them a favorite for puzzle caches, ARGs and watermarks.

To reveal a message, paste the text and CacheCrack finds it automatically. It reads messages made with StegZero (stegzero.com) and 330k's Unicode Steganography page. For 330k it tries every combination of that page's ten character checkboxes, in both Text in Text and Binary in Text mode, and offers any hidden file as a download. It reads Z.Tools messages and the one-bit format used by lorossi's zero-width-steganography script too, which hide the text as Morse code made of invisible characters. It also reads older CacheCrack messages, Unicode tag characters, emoji variation selectors, and the simple ones and zeros style used by many other tools. If the message has a passphrase, enter it to unlock it.

Hiding a message

Type the visible text, then the message. Messages are written in the same format StegZero uses, so they can be revealed with either tool. There is also an option to write them the way 330k's page does, with your own choice of its ten invisible characters, or to hide a small file, or the way Z.Tools does. The compact option packs three bits into each invisible character. The compatible option uses only the two most widely supported ones, which survive more apps but make a longer payload. The hidden characters are spread through the visible text rather than bunched at the end. A passphrase scrambles the message and checks that the reader has the right one, but it is not real encryption.

Will it survive?

Email, text files, Discord and Telegram usually keep invisible characters. Some social networks strip them out. Send yourself a test first, then paste what arrives back here to check.

Inspect and clean

Inspect lists every invisible or suspicious character with its position: zero-width characters, text direction controls, tag characters, unusual spaces, and look-alike letters from other alphabets, like a Cyrillic р hiding in an English word. Clean removes or replaces them all, which is handy before pasting puzzle text into other tools.