How to type Double Left Right Arrow
To type Double Left Right Arrow (⇔), press Alt + 8660 on Windows, holding Alt while typing the digits on the numeric keypad, or write ⇔ in HTML. On any system you can copy it from this page, or enter its codepoint U+21D4 directly: Ctrl+Shift+U then 21d4 on Linux, or 21d4 then Alt+X in Microsoft Word.
Left Right Double Arrow
- Copy it
- Unicode
- U+21D4
- Windows
- Alt + 8660 needs regedit
| Where | Shortcut | How |
|---|---|---|
| Windows | Alt + 8660 | Above 255, so Windows will not accept it as typed. Copy the character instead. |
| Mac | N/A | Press the keys together. |
| HTML | ⇔ | Paste this into HTML source. |
| Unicode | U+21D4 | LEFT RIGHT DOUBLE ARROW |
Symbols related to Double Left Right Arrow
These are filed under arrow in CLDR, the keyword list Unicode publishes alongside the names.
Other arrows symbols
⇔ lives in the Arrows block (U+2190-U+21FF), arrows in every direction and weight. Within Unicode it is classified as Sm, a mathematical symbol. Software may lay it out with the spacing an operator expects.
What Double Left Right Arrow is used for
In mathematical notation ⇔ is a relation: it makes a claim about the two things either side of it, which is true or false rather than a value to work out. TeX gives a relation more space than an operator, and breaks a long line at one in preference to breaking at an operator. That is the classification unicode-math gives it, and it is what decides how the symbol is set: $\Leftrightarrow$ in LaTeX, in maths mode rather than in a sentence.
How Double Left Right Arrow behaves in software
⇔ is East Asian Ambiguous: one column in a Western locale and two in a CJK one. That is why a table that lines up on your machine can break on somebody else's, with no change to the text at all. It carries no direction of its own, so in a line that mixes English with Arabic or Hebrew it takes the direction of the text around it rather than forcing one.
Every way to write Double Left Right Arrow
| Form | Value |
|---|---|
| Codepoint | U+21D4 |
| Decimal | 8660 |
| UTF-8 bytes | E2 87 94 |
| UTF-16 bytes | 21 D4 |
| HTML entity | ⇔ |
| HTML numeric | ⇔ or ⇔ |
| CSS | \21D4 |
| JavaScript | \u21D4 |
| Python | \u21D4 |
| URL-encoded | %E2%87%94 |
| LaTeX, in maths mode | $\Leftrightarrow$ |
| SVG | 21D4.svg · (SIL Open Font License) |
If ⇔ arrives as ⇔
Its three UTF-8 bytes E2 87 94 are being read one at a time as Windows-1252. The text is undamaged; the reader has to be told it is UTF-8.