Double-struck italic small j (ⅉ) is the Unicode character at U+2149 in the Letterlike Symbols block. Official name: DOUBLE-STRUCK ITALIC SMALL J. It is used in mathematics for quaternion notation and engineering-style imaginary j.
Remember
Character ⅉ
Unicode U+2149
Hex entity ⅉ
Decimal ⅉ
CSS escape \2149
Named entity (none)
Not the same j · ⅈ (ⅈ) · ȷ (ȷ)
Prefer ⅉ or ⅉ in HTML (no named form). You can also type ⅉ in UTF-8.
Small j using Hex Code: ⅉ
Small j using HTML Code: ⅉ
Small j using CSS Entity: ⅉ
Typed directly: ⅉ
Compared: a + bⅉ vs a + bⅈ
How It Works
1. Hex:U+2149 → ⅉ in HTML. Preferred when there is no named entity.
2. Decimal: same code point as 8521 → ⅉ. Same result as hex.
3. CSS: use \2149 in content (not an HTML entity). #point::after appends that ⅉ after the paragraph text.
4. Typed / compared: paste ⅉ in UTF-8, or contrast a + bⅉ with a + bⅈ (ⅈ).
Pitfalls & Tips
Common mistakes when working with Double Struck Italic Small J.
Name
No named entity
There is no HTML5 named entity for U+2149 (no &jj; or &ImaginaryJ;). Use ⅉ or ⅉ.
j
Not a styled letter j
Italic or bold CSS on ordinary j (U+006A) is not the same code point as U+2149. Use the Letterlike Symbol when you need this glyph.
ⅈ
Not ⅈ
ⅈ is the mathematical imaginary unit i (U+2148). U+2149 is the related double-struck italic j.
ȷ
Not ȷ
ȷ is Latin small letter dotless j with stroke (U+0237) — a different character from double-struck italic j.
CSS vs HTML
Do not mix escapes
\2149 belongs in CSS strings. ⅉ / ⅉ belong in HTML.
Fonts
Math font coverage
Some fonts omit Letterlike Symbols. Prefer a math-capable font for reliable display of ⅉ.
Semicolon
End references
Always finish numeric entities with ; — write ⅉ, not ⅉ.
Compatibility
Browser Support
Double-struck italic small j (U+2149) and its entity forms (ⅉ, ⅉ, CSS \\2149) are supported in all mainstream browsers. Visible glyphs depend on math / Letterlike Symbols font coverage.
✓ Universal support
Double Struck Italic Small J (ⅉ)
Encode with hex, decimal, CSS escape, or type the character — same code point everywhere encoding is supported.
100%Browser coverage
Google ChromeSupported
Yes
Microsoft EdgeSupported
Yes
Mozilla FirefoxSupported
Yes
Apple SafariSupported
Yes
OperaSupported
Yes
Internet ExplorerAll versions
Yes
U+2149 / entitiesFull support
Bottom line: Prefer ⅉ in HTML (no named form). Use ⅉ when decimal form is required, and \\2149 only inside CSS content.
Remember
Key Takeaways
Unicode: double-struck italic small j is U+2149 (decimal 8521) — glyph ⅉ.
HTML: no named entity — use ⅉ / ⅉ / type ⅉ.
CSS: use \2149 inside content for generated text.
Meaning:ⅉ = quaternion / engineering j — not ⅈ, not a styled letter j.
One line:U+2149 → ⅉ / ⅉ / CSS \2149 / type ⅉ.
Frequently Asked Questions
Use ⅉ (hex), ⅉ (decimal), type ⅉ directly in UTF-8, or the CSS escape \2149 in content. There is no named HTML entity for U+2149.
U+2149 (DOUBLE-STRUCK ITALIC SMALL J). Hex 2149, decimal 8521. It belongs to the Letterlike Symbols block (U+2100–U+214F).
No. Use numeric forms ⅉ or ⅉ, or type the character in a UTF-8 document. Do not confuse with ⅈ (U+2148) or ȷ (U+0237).
Use it in mathematical or scientific text for double-struck italic j — often quaternions or engineering’s imaginary j. Prefer ⅈ for the mathematical imaginary unit i (U+2148).
HTML entities (ⅉ or ⅉ) go in markup. The CSS escape \2149 goes in stylesheet strings (usually content on ::before/::after).
No. U+2149 is ⅉ. ⅈ is ⅈ (U+2148). A styled CSS italic j is still the ordinary letter U+006A — not this Letterlike Symbol.
🤔
Did you know?
Double-struck italic small j is Unicode U+2149 (decimal 8521) — glyph ⅉ in the Letterlike Symbols block. There is no HTML5 named entity; use ⅉ or ⅉ. Common uses: quaternion unit and engineering-style imaginary j. The related imaginary i is ⅈ (U+2148).
