U+21D4 · Arrows
Double Left Right Arrow ⇔
The left right double arrow expresses logical equivalence: A ⇔ B means each statement implies the other, often read aloud as "if and only if." It is common in math proofs, logic courses and definitions, and it also appears in diagrams to show a two-way relationship or a reversible exchange between two items.
Character codes
| Unicode code point | U+21D4 | |
|---|---|---|
| Decimal | 8660 | |
| HTML named entity | ⇔ | |
| HTML (hex) | ⇔ | |
| HTML (decimal) | ⇔ | |
| CSS | \21D4 | |
| JavaScript | \u21D4 | |
| Python | \u21D4 | |
| UTF-8 bytes | E2 87 94 | |
| UTF-16 | 21D4 | |
| URL-encoded | %E2%87%94 |
Character details
| Official name | LEFT RIGHT DOUBLE ARROW |
|---|---|
| Unicode block | Arrows |
| General category | Math Symbol (Sm) |
| SymbolHero category | Arrows |
| Emoji | No |
How to type ⇔
Windows
- In Microsoft Word or Outlook: type
21D4then press Alt + X. - Open Character Map (search “Character Map” in Start), tick “Advanced view”, search for “left right double arrow”, then Select and Copy.
Mac
- Press Control + Command + Space to open the Character Viewer, search “left right double arrow”, and double-click the result.
- With the Unicode Hex Input keyboard enabled (System Settings → Keyboard → Input Sources), hold Option and type
21D4.
iPhone & Android
- Tap Copy at the top of this page, then long-press where you want it and choose Paste.
Docs & web
- Google Docs: Insert → Special characters, then search “left right double arrow” or enter
U+21D4. - HTML:
⇔or⇔ - Excel / Google Sheets:
=UNICHAR(8660)
Examples
- x² = 4 ⇔ x = 2 or x = −2
- A ∩ B = A ⇔ A ⊆ B
- Online ⇔ in-store pricing match
Good to know
Don’t mix it up: Compare it with ↔ (U+2194), the single-line two-way arrow, which usually indicates direction or correspondence rather than equivalence.
Tip: Use the HTML entity ⇔ to add it to a web page.
Display: the character itself is always the same code point, but its shape comes from the font on the device showing it. If you see an empty box, the font lacks this glyph—the text is still correct.
Similar arrows
Questions
What is the Unicode for ⇔?
It is U+21D4 (LEFT RIGHT DOUBLE ARROW), decimal 8660.
Is there a Windows Alt code for it?
No standard Alt code exists for this character. In Word type 21D4 then Alt+X, or copy it from this page.
How do I type it on a Mac?
There is no built-in Option shortcut. Use the Character Viewer (Control + Command + Space) and search “left right double arrow”, or copy it from this page.
What is the HTML code?
Use the named entity ⇔ or the numeric reference ⇔.