HTML Entity for Uppercase H Double Struck (ℍ)
What You'll Learn
How to display the uppercase H double struck (ℍ) in HTML using named entity, hexadecimal, decimal, and CSS escape methods. This mathematical symbol denotes the quaternions, a number system extending the complex numbers, commonly written as ℍ in equations such as q ∈ ℍ. It is U+210D in the Letterlike Symbols block (U+2100–U+214F).
Render it with ℍ, ℍ, ℍ, or CSS escape \210D. The named entity ℍ is often the most readable option in HTML source. See also math entities.
⚡ Quick Reference — Uppercase H Double Struck Entity
U+210DLetterlike Symbols
ℍHexadecimal reference
ℍDecimal reference
ℍMost readable option
Name Value
──────────── ──────────
Unicode U+210D
Hex code ℍ
HTML code ℍ
Named entity ℍ
CSS code \210D
Meaning Double-struck capital H (quaternions)
Related U+0048 = plain H; U+0124 = Ĥ (H circumflex)
Block Letterlike Symbols (U+2100–U+214F)Complete HTML Example
A simple example showing the uppercase H double struck (ℍ) using hexadecimal code, decimal HTML code, the named entity, and a CSS content escape:
<!DOCTYPE html>
<html>
<head>
<style>
#point:after{
content: "\210D";
}
</style>
</head>
<body>
<p>Symbol (hex): ℍ</p>
<p>Symbol (decimal): ℍ</p>
<p>Symbol (named): ℍ</p>
<p id="point">Symbol (CSS): </p>
</body>
</html>🌐 Browser Support
The uppercase H double struck (ℍ) and the named entity ℍ are supported in all modern browsers:
👀 Live Preview
See the uppercase H double struck (ℍ) in mathematical notation:
🧠 How It Works
Hexadecimal Code
ℍ uses the Unicode hexadecimal value 210D to display the character. The x prefix indicates hexadecimal format.
Decimal HTML Code
ℍ uses the decimal Unicode value 8461 to display the same character. A common method for Letterlike Symbols.
Named Entity
ℍ is the standard named entity for ℍ—readable in source HTML and part of the HTML5 entity set for blackboard bold letters.
CSS Entity
\210D is used in CSS stylesheets, particularly in the content property of pseudo-elements like ::before and ::after.
Same visual result
All four methods produce the glyph: ℍ. Unicode U+210D sits in Letterlike Symbols. Do not confuse with plain H (U+0048) or Ĥ (H circumflex, U+0124). Use math-friendly fonts for best rendering.
Use Cases
The uppercase H double struck (ℍ) is commonly used in:
Denote the quaternion number system ℍ in algebra, 3D rotation math, and physics.
Represent number systems alongside ℝ (reals), ℂ (complex), and ℤ (integers) in mathematical notation.
Documentation and tutorials on rotations using quaternion mathematics in game engines and graphics APIs.
Research papers, theses, and journal articles in mathematics, robotics, and theoretical physics.
Textbooks, online courses, and tutorials explaining quaternions and blackboard bold notation.
Equation editors, calculators, and interactive math apps that render set notation in HTML.
Orientation and kinematics documentation that uses quaternion algebra for spatial rotations.
💡 Best Practices
Do
- Use
ℍin HTML when possible for readability - Serve pages as UTF-8; you can also type ℍ directly in UTF-8 source
- Use math-friendly fonts (e.g. Cambria Math, STIX Two Math) for clear double-struck rendering
- Use fonts that support Letterlike Symbols characters
- Distinguish ℍ (U+210D) from plain
H(U+0048) and Ĥ (H circumflex)
Don’t
- Substitute plain
Hwhen ℍ is required for correct mathematical notation - Confuse ℍ (double-struck) with Ĥ (H circumflex—different character)
- Put CSS escape
\210Din HTML text nodes - Assume all fonts render Letterlike Symbols identically
- Omit UTF-8 encoding on pages with mathematical symbols
Key Takeaways
Four references render ℍ; named entity is most readable
ℍ ℍ ℍFor CSS stylesheets, use the escape in the content property
\210DUnicode U+210D — DOUBLE-STRUCK CAPITAL H
Essential for quaternions, set theory, and mathematical content
Previous: Uppercase H Circumflex (Ĥ) Next: Uppercase H Latin
❓ Frequently Asked Questions
ℍ (named), ℍ (hex), ℍ (decimal), or \210D in CSS content. The named entity ℍ is the most readable for HTML content.U+210D (DOUBLE-STRUCK CAPITAL H). Letterlike Symbols block. Hex 210D, decimal 8461. Commonly used to represent the quaternions.ℍ or ℍ) or the named entity ℍ is used in HTML content. The CSS entity (\210D) is used in CSS, e.g. in the content property of pseudo-elements. Both produce ℍ but in different contexts.Explore More HTML Entities!
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