HTML Entity for Double Struck Italic Small J (ⅉ)

Beginner
⏱️ 5 min read
📚 Updated: Jun 2026
🎯 1 Code Example
Unicode U+2149
HTML entity for Double Struck Italic Small J (U+2149) tutorial illustration

What You'll Learn

How to display the Double Struck Italic Small J (ⅉ) in HTML using hexadecimal, decimal, and CSS escape methods. This character is U+2149 (DOUBLE-STRUCK ITALIC SMALL J) in the Letterlike Symbols block (U+2100–U+214F)—used in mathematics (e.g. quaternions) and engineering notation.

Render it with ⅉ, ⅉ, or CSS escape \2149. There is no named HTML entity for U+2149. For imaginary unit i use ⅈ (U+2148, ⅈ). See also math entities.

⚡ Quick Reference — Double Struck Italic Small J

Unicode U+2149

Letterlike Symbols block

Hex Code ⅉ

Hexadecimal reference

HTML Code ⅉ

Decimal reference

Named Entity —

Not available for U+2149

Reference Table
Name           Value
────────────   ──────────
Unicode        U+2149
Hex code       ⅉ
HTML code      ⅉ
Named entity   —
CSS code       \2149
Related        U+2148 = Small i (ⅈ)
1

Complete HTML Example

This example demonstrates the Double Struck Italic Small J (ⅉ) using hexadecimal code, decimal HTML code, and a CSS content escape. There is no named HTML entity:

html
<!DOCTYPE html>
<html>
<head>
 <style>
  #point:after{
   content: "\2149";
  }
 </style>
</head>
<body>
<p>Double Struck Italic Small J using Hexadecimal: &#x2149;</p>
<p>Double Struck Italic Small J using HTML Code: &#8521;</p>
<p id="point">Double Struck Italic Small J using CSS Entity: </p>
</body>
</html>
Try it Yourself

🌐 Browser Support

U+2149 is widely supported in modern browsers when rendered with a font that includes Letterlike Symbols:

Chrome 1+
Firefox 1+
Safari 1+
Edge 12+
Opera 4+
Android 4.4+
iOS Safari 1+

👀 Live Preview

See the Double Struck Italic Small J (ⅉ) in mathematical notation:

Large glyph ⅉ
Small i vs small j ⅈ i   ⅉ j
No named entity use &#x2149; or &#8521;
Numeric refs &#x2149; &#8521;
CSS escape \2149

🧠 How It Works

1

Hexadecimal Code

&#x2149; uses the Unicode hexadecimal value 2149 to display the Double Struck Italic Small J. The x prefix indicates hexadecimal format.

HTML markup
2

Decimal HTML Code

&#8521; uses the decimal Unicode value 8521 to display the same character.

HTML markup
3

CSS Entity

\2149 is used in CSS stylesheets, particularly in the content property of pseudo-elements like ::before and ::after.

CSS stylesheet
=

Same visual result

All three methods produce: ⅉ. Unicode U+2149. Imaginary i: &ii; (ⅈ, U+2148). No named entity for U+2149.

✅

Use Cases

The Double Struck Italic Small J (ⅉ) commonly appears in:

📐 Quaternion notation

Mathematics where ⅉ denotes a quaternion unit (with ⅈ and k) in quaternion algebra and 3D rotations.

🔬 Electrical engineering

Conventions using j for the imaginary unit; ⅉ can denote this in double-struck form.

📚 Academic publishing

Textbooks, papers, and course materials requiring letterlike math symbols in HTML.

💻 Math on the web

Equation editors and math rendering alongside other double-struck italic letters.

📖 Unicode references

Entity lists and guides for Letterlike Symbols (U+2100–U+214F).

♿ Accessibility

Use math-capable fonts so ⅉ renders clearly for all readers.

💡 Best Practices

Do

  • Use &#x2149; or &#8521; for ⅉ
  • Use math fonts (Cambria Math, STIX Two Math) for reliable rendering
  • Distinguish ⅉ (j) from ⅈ (&ii;, imaginary i)
  • Use \2149 only inside CSS content
  • Keep entity style consistent across the document

Don’t

  • Assume a named entity exists for U+2149—it does not
  • Use &ii; when you need small j ⅉ
  • Put CSS escape \2149 in HTML text nodes
  • Forget UTF-8 (<meta charset="utf-8">) on math pages
  • Assume every font includes Letterlike Symbols

Key Takeaways

1

No named entity—use numeric references

&#x2149; &#8521;
2

For CSS stylesheets, use the escape in the content property

\2149
3

Unicode U+2149 DOUBLE-STRUCK ITALIC SMALL J

4

Small i: ⅈ via &ii; or &#x2148;

5

Three methods, one glyph — widely supported in modern browsers

❓ Frequently Asked Questions

Use &#x2149; (hex), &#8521; (decimal), or \2149 in CSS content. All produce ⅉ. There is no named HTML entity for U+2149.
U+2149 (DOUBLE-STRUCK ITALIC SMALL J). Letterlike Symbols block (U+2100–U+214F). Hex 2149, decimal 8521. Double-struck italic form of Latin small letter j.
When you need the double-struck italic small j in mathematical or engineering content: quaternion notation, electrical engineering, expressions, or academic papers requiring this letterlike symbol.
HTML numeric references (&#8521; or &#x2149;) go in markup. The CSS escape \2149 is used in stylesheets, typically in the content property of pseudo-elements.
Letterlike symbols like &ii;, &ee;, and &dd; have named entities, but U+2149 does not. Use numeric codes or CSS. For imaginary unit i use &ii; (U+2148, ⅈ).

Explore More HTML Entities!

Discover 1500+ HTML character references — math symbols, letterlike glyphs, and more.

All HTML Entities →

About the author

Mari Selvan M P
Mari Selvan M P 🔗

Developer, cloud engineer, and technical writer

  • Experience 12 years building web and cloud systems
  • Focus Full Stack Development, AWS, and Developer Education

I write practical tutorials so students and working developers can learn by doing—from databases and APIs to deployment on AWS.

AWS Certified Developer – Associate (Credly)

8 people found this page helpful

Double Struck Italic Small I (ⅈ) Double Struck N-Ary Summation