How Unicode fancy text actually works
Why bold and script text pastes anywhere without a font, which Unicode blocks power each style, and where the letters have gaps.
Styles are characters, not formatting
When you make a word bold in a document, the letters stay the same and the app records styling around them. Fancy text works the opposite way: there is no formatting, only different characters. The bold F you copy is not the letter F with a bold attribute; it is a separate Unicode character named Mathematical Bold Capital F that happens to look like a heavy F. That is why the look survives a paste into a plain username field, which cannot store any formatting at all.
The Mathematical Alphanumeric Symbols block
Most styles draw from a block of Unicode designed for mathematicians who need bold, italic, script, fraktur, monospace, and double-struck letters to mean different things in equations. Each variant is a contiguous run of code points for A-Z and a-z, so the tool simply offsets your letter by a fixed distance to land on the styled version. Bold capitals begin at U+1D400, for instance, and lowercase and digits follow their own starting points. Circled letters come from Enclosed Alphanumerics and fullwidth letters from the Halfwidth and Fullwidth Forms block instead.
Why some letters are missing or reused
The math block has holes because a handful of letters were already encoded elsewhere in the Letterlike Symbols block. Script capital B, E, F, H and several others live at their historical positions, and this tool patches each gap so the word still looks consistent. Small caps relies on phonetic alphabet characters that never included a small q or x, so those two stay lowercase. Upside down uses a grab bag of rotated look-alikes drawn from many scripts, and any character without one is passed through unchanged.
Practical limits to keep in mind
Because these are unusual characters, support varies. A modern browser and operating system render them fine, but an older device may show empty boxes if its fonts lack those code points. Screen readers frequently mispronounce or ignore them, and some sites filter them out of display names or exclude them from search results. Treat fancy text as decoration for short, non-essential accents, and keep anything that must be read, searched, or accessible in ordinary letters.