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How LinkedIn "Bold" Text Actually Works (It's Not Bold At All)

#productivity #webdev #career #javascript

LinkedIn has no bold, italic, or strikethrough button. Yet you constantly see posts with fake bold headers and slanted emphasis. Ever wondered how that actually works?

It's not formatting, it's a different alphabet

Unicode has a block called Mathematical Alphanumeric Symbols (U+1D400 to U+1D7FF). It contains a fully separate set of letters and digits that just happen to render as bold, italic, script, or monospace, because they were designed for math notation, not chat apps.

So when a tool "bolds" your LinkedIn text, it isn't applying a style. It's swapping each character for its bold Unicode twin:

A -> Mathematical bold capital A (U+1D5D4)
a -> Mathematical bold small a (U+1D5EE)
1 -> Mathematical bold digit one (U+1D7ED)
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A minimal JS version of the mapping looks like this:

const BOLD_MAP = {
  A: '\u{1D5D4}', B: '\u{1D5D5}', C: '\u{1D5D6}',
  a: '\u{1D5EE}', b: '\u{1D5EF}', c: '\u{1D5F0}',
};

function toBoldUnicode(str) {
  return [...str].map(ch => BOLD_MAP[ch] ?? ch).join('');
}
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LinkedIn's editor has no idea any of this happened. As far as it's concerned, you just pasted some exotic characters. It renders them like any other glyph, and there's your "bold" headline.

The catches nobody mentions

  • Accessibility: screen readers often can't pronounce these characters correctly, because they aren't semantically bold, they're a separate codepoint that happens to look bold. Someone using a screen reader may hear garbled text instead of your headline.
  • Search: since these aren't the "real" letters, search engines and LinkedIn's own search sometimes fail to match your exact phrase.
  • Copy-paste breakage: paste this text into a plain text field, a code editor, or certain apps, and you'll sometimes get missing glyphs instead of your text.

Worth knowing before you bold your entire headline for the algorithm.

Where I've used this

I built a free LinkedIn text formatter (https://www.theboldloom.com/linkedin-text-formatter/) that does this conversion, bold, italic and a few other styles, in the browser. No extension, no account. Useful if you want the effect without hand-rolling the character map yourself.

Curious if anyone else has hit the accessibility or search issues above in practice. Let me know in the comments.

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