Left Right Double Arrow Symbol

A symbol from the Arrow Symbols collection. Click the symbol or the button below to copy.

Symbol: ⇔
Unicode: U+21D4
HTML entity: ⇔
Category: Arrow Symbols

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15 of 84 in the arrow symbols collection

About the left right double arrow symbol

The character ⇔ is read as “if and only if” in logic and mathematics. It represents a bidirectional logical equivalence, meaning that the statements on either side of the symbol imply each other. In formal logic, it is the biconditional operator, often used in proofs and truth tables to show that two propositions are logically equivalent.

Outside of strict logic, this double arrow appears in texts to denote a mutual dependency or a two-way relationship, such as in set theory for one-to-one correspondences or in diagrams to indicate reversible processes. It is distinct from the single-headed double arrow (⇌), which typically marks chemical equilibrium.

How to type Left Right Double Arrow

Native keyboard shortcuts for each operating system — derived from the codepoint, so the steps below are always accurate.

Windows

2 options

In Word / Outlook: type 21D4 then press Alt + X.
Anywhere: press Win + . to open the emoji & symbol picker, then search.

macOS

2 options

Enable “Unicode Hex Input” in System Settings → Keyboard, then hold Option and type 21D4.
Or: Control + Command + Space opens the Character Viewer — search by name.