Double Left Right Arrow (⇔)

The double left right arrow ⇔ is Unicode U+21D4, the “if and only if” arrow from logic. Press Copy to put it on your clipboard.

Unicode: U+21D4
HTML: ⇔
Word: 21D4 Alt+X

How to type the double left right arrow (⇔)

The quickest way is to press Copy above and paste. To type ⇔ yourself, use the method for your device below.

Windows

In Word or Outlook, type 21D4 and press Alt + X. Alt + X converts the hex code before the cursor into the character, and back again.
Press Win + R, type charmap and press Enter. Tick “Advanced view”, search for Left Right Double Arrow, then Select and Copy. Character Map is built into every version of Windows.

Mac

Press Control + Command + Space to open the Character Viewer, search for left right double arrow and double-click it.
With the Unicode Hex Input keyboard enabled (System Settings → Keyboard → Input Sources), hold Option and type 21D4.

Linux & ChromeOS

Press Ctrl + Shift + U, type 21d4, then press Enter or Space. Works in GTK and IBus apps (GNOME, Firefox, Chrome, LibreOffice) and on ChromeOS.

iPhone & iPad

Copy ⇔ from this page, then go to Settings → General → Keyboard → Text Replacement and add it with a shortcut such as ;doub. The shortcut then turns into the symbol as you type, in every app.

Android

Copy ⇔ here, then open Gboard settings → Dictionary → Personal dictionary and add it with a shortcut.

Microsoft Word

Type <=> and Word's AutoCorrect replaces it with ⇔.
Type 21D4, then press Alt + X.
Insert → Symbol → More Symbols. Set “from” to Unicode (hex), type 21D4 in “Character code” and click Insert.

Google Docs

Insert → Special characters, then search for “left right double arrow” or draw it in the box.

Excel & Google Sheets

Enter =UNICHAR(8660) in a cell. It works in Excel 2013 and later and in Google Sheets.

HTML

Write ⇔ or ⇔ in your HTML.

What does ⇔ mean?

The double left right arrow ⇔ means if and only if (often shortened to “iff”): the statements on each side are logically equivalent, so each implies the other. For example, “a triangle is equilateral ⇔ all its angles are 60°”. Word replaces <=> with ⇔ automatically, and the HTML entity is ⇔.

Common uses

Proofs: x² = 9 ⇔ x = 3 or x = −3
Truth tables: the biconditional P ⇔ Q

Double Left Right Arrow codes for HTML, CSS and programming

Every code below produces ⇔. Use the HTML entity in web pages, the CSS escape in content, and the escape sequence in source code.

Codes for ⇔
Unicode code point	`U+21D4`
HTML entity (named)	`⇔`
HTML decimal	`⇔`
HTML hex	`⇔`
CSS content	`content: "\21D4";`
JavaScript	`"\u21D4"`
Python	`"\u21D4"`
Python (by name)	`"\N{LEFT RIGHT DOUBLE ARROW}"`
Java / C#	`"\u21D4"`
LaTeX	`\Leftrightarrow`
UTF-8 bytes	`E2 87 94`
UTF-16	`21D4`
URL encoded	`%E2%87%94`

⇔ vs look-alike characters

These characters look similar to ⇔ but have a different meaning and code. Pasting the wrong one can break search, sorting and screen readers.

Char	Name	When to use it
	Long Left Right Double Arrow `U+27FA`	Long left right double arrow (U+27FA), the display-size “iff”.
	Identical to `U+2261`	Identical to, used for logical equivalence in some texts.
	Left Right Arrow `U+2194`	Single-line left right arrow.

Symbols similar to ⇔

Click to copy, or open a symbol for its codes. See the full arrow symbols collection.

⇔ character properties

Official Unicode name: LEFT RIGHT DOUBLE ARROW
Also known as: if and only if symbol, iff symbol, equivalence arrow
Code point: U+21D4
Unicode block: Arrows (U+2190–U+21FF)
General category: Math symbol (Sm)
Added in: Unicode 1.1 (1993)
Plane: Basic Multilingual Plane (0)
Emoji: No, it is a text symbol

Frequently asked questions

What does iff mean?

“Iff” is short for “if and only if”, written ⇔. It means both statements are true together or false together.

Is there an alt code for the double left right arrow?

No. ⇔ is outside the Windows-1252 and code page 437 character sets, so no Alt + number code produces it. Copy it from this page, type 21D4 then Alt + X in Word, or find it in Character Map.

How do I type the double left right arrow on a Mac?

There is no single Option shortcut for ⇔ on the US layout. Press Control + Command + Space to open the Character Viewer, search for “left right double arrow” and double-click it, or copy it from this page.

What is the HTML code for the double left right arrow?

Use the named entity ⇔ or the numeric reference ⇔ (hex ⇔). All three display ⇔ in every browser.

What is the Unicode for the double left right arrow?

⇔ is U+21D4, officially named LEFT RIGHT DOUBLE ARROW, in the Arrows block. It has been part of Unicode since version 1.1 (1993).