HTML Entity for Left Right Double Arrow (⇔)
What You'll Learn
How to display the Left Right Double Arrow (⇔) in HTML using the named entity, hexadecimal, decimal, and CSS escape methods. This symbol is U+21D4 (LEFT RIGHT DOUBLE ARROW) in the Arrows block (U+2190–U+21FF)—a bidirectional double arrow used for equivalence, reversible relations, logical iff, and two-way navigation in logic, mathematics, and UI.
Render it with ⇔ (named), ⇔, ⇔, or CSS \21D4. Do not confuse ⇔ with U+2194 (↔, single left right arrow / ↔) or U+21CE (⇎, left right double arrow with stroke).
⚡ Quick Reference — Left Right Double Arrow
U+21D4Arrows block
⇔Hexadecimal reference
⇔Decimal reference
⇔Most readable option
Name Value
──────────── ──────────
Unicode U+21D4
Hex code ⇔
HTML code ⇔
Named entity ⇔
CSS code \21D4
Meaning Left right double arrow (equivalence)
Related U+2194 = left right arrow (↔)
U+21CE = double arrow with stroke (⇎)Complete HTML Example
A simple example showing the Left Right Double Arrow (⇔) using the named entity, hexadecimal code, decimal HTML code, and a CSS content escape:
<!DOCTYPE html>
<html>
<head>
<style>
#point:after{
content: "\21D4";
}
</style>
</head>
<body>
<p>Arrow (hex): ⇔</p>
<p>Arrow (decimal): ⇔</p>
<p>Arrow (named): ⇔</p>
<p id="point">Arrow (CSS): </p>
</body>
</html>🌐 Browser Support
The Left Right Double Arrow (⇔) is universally supported in all modern browsers when the font includes Arrows block glyphs:
👀 Live Preview
See the Left Right Double Arrow (⇔) rendered live in different contexts:
🧠 How It Works
Hexadecimal Code
⇔ uses the Unicode hexadecimal value 21D4 for the left right double arrow. The x prefix indicates hexadecimal format.
Decimal HTML Code
⇔ uses the decimal Unicode value 8660 to display the same character.
Named Entity
⇔ is the semantic named entity — the easiest to read in source HTML and the most self-descriptive option.
CSS Entity
\21D4 is used in CSS stylesheets in the content property of pseudo-elements like ::after.
Same visual result
All four methods produce ⇔. Unicode U+21D4 is in the Arrows block. Previous: Left Right Arrow Vertical Stroke.
Use Cases
The Left Right Double Arrow (⇔) is commonly used in:
Indicate logical equivalence (e.g. A ⇔ B) in formal logic and proofs.
Denote “if and only if” (iff) or bidirectional implication.
Show two-way navigation, expand/collapse, or bidirectional controls.
Indicate reversible mappings, two-way sync, or equivalence in specs.
Use in papers for equivalence and bidirectional relation notation.
Represent two-way flow or symmetric relations between nodes.
💡 Best Practices
Do
- Use
⇔for readable source markup - Add
aria-labelor surrounding text for accessibility - Verify your font supports the Arrows block (U+21D4)
- Keep one entity style per project for consistency
- Provide context when the symbol denotes equivalence or two-way relation
Don’t
- Confuse ⇔ (double arrow) with ↔ (single left right arrow)
- Use CSS
\21D4inside HTML text nodes - Assume all fonts render the double arrow identically
- Mix entity styles randomly in one file
- Use the symbol without explaining equivalence meaning on first use
Key Takeaways
Three HTML references plus CSS all render ⇔
⇔ ⇔ ⇔For CSS, use \21D4 in the content property
Unicode U+21D4 — LEFT RIGHT DOUBLE ARROW
Prefer ⇔ for readability—it’s the named HTML entity
Previous: Left Right Arrow Vertical Stroke Next: Left Right Double Arrow Stroke
❓ Frequently Asked Questions
⇔ (hex), ⇔ (decimal), ⇔ (named), or \21D4 in CSS content. All four methods render ⇔ correctly.U+21D4 (LEFT RIGHT DOUBLE ARROW). Arrows block (U+2190–U+21FF). Hex 21D4, decimal 8660. Used for bidirectional double arrows, often meaning equivalence or reversible relation.⇔, ⇔, or ⇔) go in markup. The CSS escape \21D4 is used in stylesheets, typically on ::before or ::after. Both produce ⇔.⇔ is the named HTML entity for U+21D4. You can also use ⇔ (decimal) or ⇔ (hex) and \21D4 in CSS.Explore More HTML Entities!
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