Why invisible characters matter
Zero-width spaces and joiners break search, passwords, code and spreadsheet formulas without showing up on screen. Text copied from web pages, chat apps, PDFs and AI tools often carries them. Direction marks can make code read differently from how it runs, a trick known as Trojan Source.
Lookalike letters
Some Cyrillic and Greek letters look exactly like Latin ones, so a word such as pаypal can be spelled with a Cyrillic а. Phishing links and spoofed usernames use this. Text that mixes alphabets in one word is flagged.
Bytes and encodings
Each character shows its UTF-8 and UTF-16 bytes, plus the HTML and JavaScript escapes, so you can track down encoding bugs and copy exact escapes into code.