Caution Sign (☡) is the Unicode character at U+2621 in the Miscellaneous Symbols block (official name: CAUTION SIGN). In mathematics it is widely known as the Bourbaki dangerous bend mark — a warning that a passage needs care.
Remember
Character ☡
Unicode U+2621
Hex entity ☡
Decimal ☡
CSS escape \2621
Named entity (none)
All of these produce the same glyph: ☡. Prefer ⚠ (U+26A0) for general UI warnings; use ☡ when you specifically need the caution / Bourbaki mark.
Reference
Quick Reference
One table for every form you will actually use.
Form
Code
Where it goes
Direct character
☡
HTML text (UTF-8)
Hex entity
☡
HTML markup
Decimal entity
☡
HTML markup
CSS escape
\2621
Stylesheet content
Named entity
—
Not defined in HTML5
When to use which
Situation
Use
Need the caution / Bourbaki glyph ☡
Type ☡, or ☡ / ☡
Generated text via ::before / ::after
content: "\2621"
General UI warning / alert
Prefer ⚠ (U+26A0)
Looking for &caution; or similar
Does not exist — use numeric form
See it
Live Preview
Caution Sign rendered in common writing contexts.
Inline text☡ Read carefully
Large glyph☡
Compared☡ ⚠ ☢
Monospacenote ☡ → caution
With entitiesHex: ☡ | Decimal: ☡
Code
Complete HTML Example
One page that shows Caution Sign with the hex entity, decimal entity, CSS escape, and a typed character. Use View Output or open the live editor.
Hex + Decimal + CSS + Typed
All four ways to produce ☡ in a single document.
html
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Caution Sign (☡) in HTML</title>
<style>
#point::after {
content: "\2621";
}
</style>
</head>
<body>
<p>Caution Sign using Hex Code: ☡</p>
<p>Caution Sign using HTML Code: ☡</p>
<p id="point">Caution Sign using CSS Entity: </p>
<p>Typed directly: ☡</p>
</body>
</html>
Caution Sign using Hex Code: ☡
Caution Sign using HTML Code: ☡
Caution Sign using CSS Entity: ☡
Typed directly: ☡
How It Works
1. Hex:U+2621 → ☡ in HTML. The browser turns it into ☡.
2. Decimal: same code point as 9761 → ☡. Same result as hex.
3. CSS: use \2621 in content (not an HTML entity). #point::after appends that ☡ after the paragraph text.
4. Typed ☡: fine in UTF-8 pages. All four lines show the same glyph.
Pitfalls & Tips
Common mistakes when working with Caution Sign entities.
Named?
No named entity
HTML5 does not define &caution; or similar. Use numeric forms.
CSS vs HTML
Do not mix escapes
\2621 belongs in CSS. ☡ / ☡ belong in HTML.
☡ vs ⚠
Different characters
☡ is U+2621 (caution / Bourbaki). Warning sign ⚠ is U+26A0.
Meaning
Pick the right warning
For app alerts and safety UI, prefer ⚠. Use ☡ for math/academic “dangerous bend” notes.
Fonts
Check the glyph
Miscellaneous Symbols coverage varies. If ☡ is missing, use a fallback font or plain text “caution.”
Semicolon
End references
Always finish with ; — write ☡, not ☡.
Compatibility
Browser Support
Caution Sign (U+2621) and its numeric entity forms (☡, ☡, CSS \\2621) are supported in all mainstream browsers. Glyph shape depends on the font.
✓ Universal support
Caution Sign (☡)
Encode with hex, decimal, or CSS escape — or paste ☡ in UTF-8 HTML.
100%Browser coverage
Google ChromeSupported
Yes
Microsoft EdgeSupported
Yes
Mozilla FirefoxSupported
Yes
Apple SafariSupported
Yes
OperaSupported
Yes
Internet ExplorerAll versions
Yes
U+2621 / entitiesFull support
Bottom line: Use ☡ or ☡ for the Unicode glyph, and \\2621 only inside CSS content. Prefer ⚠ for general UI warnings.
Remember
Key Takeaways
Unicode: caution sign is U+2621 (decimal 9761).
HTML: use ☡ or ☡ when you need an entity.
One line:U+2621 → ☡ / ☡ / CSS \2621, or paste ☡.
Frequently Asked Questions
Use ☡ (hex), ☡ (decimal), or the CSS escape \2621 in the content property. All render ☡. You can also paste ☡ directly when your file is UTF-8.
U+2621 (hex 2621, decimal 9761). Unicode names it CAUTION SIGN. It belongs to the Miscellaneous Symbols block.
No. HTML5 does not define a named entity for ☡. Use numeric references like ☡ or ☡.
☡ (U+2621) is the caution / Bourbaki dangerous-bend mark. ⚠ (U+26A0) is WARNING SIGN — the common triangle warning glyph used in UI.
HTML entities (☡ or ☡) go in markup. The CSS escape \2621 is used in stylesheets (usually in the content property of ::before/::after). Both render ☡.
Use it in math notes, textbooks, or when you specifically need the Bourbaki caution mark. Prefer ⚠ for general UI warnings and alerts.
🤔
Did you know?
Caution sign is Unicode U+2621 (decimal 9761) — official name CAUTION SIGN in the Miscellaneous Symbols block. HTML5 has no named entity. In mathematics it is often called the Bourbaki “dangerous bend” mark and is not warning sign (U+26A0 ⚠).
