They are not fonts
Bios, captions and usernames have no font settings, so fancy text generators swap each letter for a different character that looks like a styled letter. Unicode, the standard every device uses for text, includes whole alphabets of bold, italic, script, double-struck and Fraktur letters for use in mathematics, as well as circled and fullwidth letters. 𝐀 (mathematical bold A) is a different character from A, in the same way that a digit 1 is different from a letter l.
Where it works
Because they are ordinary characters, they paste into Instagram bios and captions, TikTok, Discord, X, YouTube comments and most other places that accept text, and they look the same to everyone whose device has the characters in its fonts.
Where it breaks
- Missing characters. Older devices and some fonts show empty boxes instead.
- Search. Search engines and in-app search usually treat 𝐬𝐚𝐥𝐞 as different from sale, so styled words may not be found.
- Usernames and forms. Most sites only allow plain letters in usernames, emails and passwords.
- Screen readers. They may read each letter as "mathematical bold small s" or skip it, which makes posts hard to follow for blind and partially sighted readers.
Use it sparingly
Style a name or a short heading, and keep the message itself in plain text so everyone can read and find it. Upside-down text is fun but often unreadable for screen readers. If a platform counts characters, some styled letters take up two units each, so check the length with the Character Counter.
Make styled text with the Fancy Text Generator, and change normal capitalization with the Case Converter.