Code point
U+21D4
Glyph appearance depends on your fonts.
U+21D4
SmU+21D4 LEFT RIGHT DOUBLE ARROW is a Unicode 16.0.0 character in the Math Symbol category. It belongs to the Arrows block.
Choose the representation you need, then copy its value.
U+21D4
8660
⇔
⇔
⇔
E2 87 94
21D4
000021D4
%E2%87%94
\u21D4
\u21D4
\u21D4
\21D4