Mathematical Bold Digit Zero

It is zero in a bold mathematical style.

In a formula, a bold 0 may have a different role from an unstyled 0. A 1999 proposal from STIX, a collaboration of scientific and technical publishers, called for complete bold, italic, and other mathematical alphabets so plain text could preserve such distinctions. It extended a smaller, already encoded group of math-style characters into fuller alphabets that included digits. The numeral still means zero; the formula gives it its particular role.

Is 𝟎 just a bold 0?

No. It is a separate character, not a style switch.

Unicode intended mathematical alphabets for formulas and technical notation. As of 2026, people also use characters such as 𝟎 for playful bold styling on social media where rich-text formatting is unavailable. The same characters can be used to get around keyword filters, so they do not reliably hide a word.

Why can 𝟎 turn into 0?

Compatibility normalization can remove its bold distinction.

Unicode compatibility normalization, called NFKC, turns 𝟎 into plain 0. Software that applies it can erase a distinction your formula relies on.

For equations rendered with MathJax 4.0, a missing math-font glyph can trigger fallback to another font, so the weight may look different from nearby symbols.