Ordinary bold formatting (like Markdown's **bold**) depends on the app interpreting formatting codes, it disappears the moment you paste it somewhere that only accepts plain text. This tool sidesteps that by mapping each letter and digit onto the Unicode "Mathematical Bold" block, a set of visually bold look-alike characters that are part of the character itself, not a style applied on top. That means the boldness survives copy-pasting into places like Instagram bios, WhatsApp, or Discord usernames where real bold formatting isn't available, the tradeoff is that screen readers may pronounce these differently since they're technically distinct symbols, not styled Latin letters.
Markdown bold is just formatting syntax that a specific app interprets and renders, paste it into a plain-text field and you'll just see the literal asterisks, because there's no separate 'bold' character being sent.
Not always, because these are distinct Unicode math symbols rather than styled Latin letters, some screen readers may skip them or read them oddly, so avoid using Unicode bold for essential accessibility content.
Yes, digits 0–9 have their own bold Unicode equivalents, so a bold heading with numbers in it will convert cleanly along with the letters.