U+21D4 · Math symbol
HTML entity
⇔
LaTeX
\Leftrightarrow
Left Right Double Arrow Symbol ⇔
⇔ is left right double arrow. Write it in HTML as ⇔ or paste the character directly. It was added in Unicode 1.1, and Unicode files it under Math symbol.
Codes & technical data
| Unicode | U+21D4 | |
|---|---|---|
| HTML hex | ⇔ | |
| HTML decimal | ⇔ | |
| CSS | \21D4 | |
| JavaScript | \u{21D4} | |
| Python | \U000021D4 | |
| Java / C# | \u21D4 | |
| Rust | \u{21d4} | |
| Swift | \u{21D4} | |
| PHP | \u{21D4} | |
| URL encoded | %E2%87%94 | |
| UTF-8 bytes | E2 87 94 | |
| UTF-16 bytes | 21D4 | |
| Base64 | 4oeU | |
| Decimal | 8660 | |
| HTML entity | ⇔ | |
| LaTeX | \Leftrightarrow | |
| Category | Math symbol (Sm) | |
| Introduced | Unicode 1.1 | |
Will ⇔ survive being pasted?
- Normalisation. Yes. ⇔ is unchanged by NFKC, so it survives normalising systems intact.
- Legacy encodings. ⇔ is Unicode-only — it has no Latin-1 equivalent, so a system stuck on an 8-bit encoding cannot represent it.
- Size. 3 bytes in UTF-8. Character-limited fields — SMS, bios, some form validators — usually count bytes, not characters.
Other arrow characters
Unicode names 24 characters ending in “arrow”. They differ by direction, weight or decoration rather than by meaning.
Nearby in Arrows
The core arrow set: every direction, plus doubled, dashed, hooked and looped variants. Anything not here is in one of the four supplemental arrow blocks, which exist because this one filled up.
How to type ⇔
| Windows | Type 21D4 then press Alt+X |
|---|---|
| macOS | Press Ctrl+Cmd+Space, then search for “left right double arrow” |
| Linux | Press Ctrl+Shift+U, type 21d4, press Enter |
| HTML | ⇔ |
About Unicode’s Math symbol category
Unicode classifies this as a mathematical symbol, which means software that lays out formulas treats it as an operator or relation and gives it spacing accordingly, rather than setting it tight against its neighbours like a letter.
Frequently asked questions
- How do I type the ⇔ left right double arrow symbol?
- On Windows, type 21D4 and press Alt+X. On Linux press Ctrl+Shift+U then 21d4. On any system the quickest route is the copy button on this page.
- What is the code for ⇔?
- Left Right Double Arrow is U+21D4, written in HTML as ⇔ and in LaTeX as \Leftrightarrow. In UTF-8 it takes 3 bytes. The table above lists every escape format.
- What kind of character is ⇔?
- Left Right Double Arrow is filed under Math symbol in the Arrows block, and was introduced in Unicode 1.1. Unicode classifies this as a mathematical symbol, which means software that lays out formulas treats it as an operator or relation and gives it spacing accordingly, rather than setting it tight against its neighbours like a letter.