Characters, not fonts
Every character you can type has a number in the Unicode Standard, called a code point. The capital letter A is U+0041. A font is a separate thing: a file of drawings that tells a device how to draw each code point.
When you make text bold in a word processor, the letters stay the same code points and the app tells the font to use its bold drawings. When you use a fancy text generator, something different happens. The generator replaces your A with a different code point, such as U+1D400, whose official name is MATHEMATICAL BOLD CAPITAL A. Your device draws that character with whatever font it has that includes it.
That is why people call them Unicode fonts, even though nothing about the font changed. The style is built into the characters themselves.
Where these characters came from
Most styled alphabets come from the Mathematical Alphanumeric Symbols block, added in Unicode 3.1. Mathematicians use letter style to carry meaning. A bold x and an italic x can stand for different things in the same formula, so they need to survive as separate characters even in plain text.
Unicode encoded complete alphabets for that purpose: bold, italic, bold italic, script, bold script, Fraktur, bold Fraktur, double-struck, sans-serif variants, and monospace. A few letters had already been encoded earlier in the Letterlike Symbols block, such as the script capital B and the Fraktur capital C, so the math block leaves reserved gaps at those positions.
Other popular styles come from other places:
- Circled and parenthesized letters come from enclosed alphanumerics, used for list markers and labels.
- Fullwidth letters come from East Asian typography, where Latin letters are set to the width of ideographs.
- Small capitals and superscript letters come from phonetic notation used by linguists.
What the Unicode Consortium says
Unicode Technical Report #25 notes that the mathematical alphanumeric characters should not be used as a substitute for styling markup. In other words, they were designed for math, not for decorating a bio. Using them that way is not forbidden, and the characters are perfectly valid text, but it comes with side effects worth knowing.
What changes when your text is made of styled characters
- It keeps its look where formatting is stripped. That is the main reason people use it. Bios, display names, and comment boxes usually remove bold or italic formatting, but they keep characters.
- It stops matching normal words. ๐๐๐ญ and cat are different strings. Search, hashtags, spell check, and translation tools usually treat the styled version as unrelated characters.
- It may sound strange to screen readers. Some read each letter by its name, and some skip characters they do not know.
- It depends on the readerโs fonts. If a device has no font with a character, it shows an empty box instead. See why fancy text shows boxes.
- Some letters do not exist. There are no italic digits and no small capital x, among other gaps. See why some letters stay plain.
How FontBlaze builds its styles
FontBlaze looks up every styled character by its official Unicode name in the Unicode Character Database, instead of computing positions with arithmetic. That catches the reserved gaps automatically and makes sure every character is real and named. Characters newer than Unicode 11.0 are left out on purpose, because recently added characters often show up as boxes. You can see the code points behind any text in the Unicode inspector.
When to use real formatting instead
If the place you are writing has bold and italic buttons or supports Markdown, use them. Real formatting keeps text searchable and accessible. Unicode styled characters are the right tool for the places that have no formatting at all, and even there, a little goes a long way.