What ＃ means
The wide hash reflects older East Asian encoding widths.
Some older East Asian encodings gave characters two display cells while ASCII used one. The fullwidth form preserved that grid and helped convert legacy text.
In English, # can mark a number, abbreviate the weight unit pound, label a telephone key, or introduce a tag. A Japanese layout guide published in 2007 also lists ＃ as a note marker.
Don't confuse it with
2Questions people ask
1Why does ＃ show as a box on some devices?
Because that device's fonts have no glyph for it. The character is still correct and still copies correctly — the box is a missing glyph, not a broken character.
How to type ＃
Windows (Word)
Alt+XType FF03, then Alt+X to get ＃.
Windows
Win+Rrun charmap for the full table, or use the emoji picker's Ω symbols tab (Win + .).
macOS
Control+Command+SpaceOpen the character viewer and search “fullwidth number sign”.
Linux
Ctrl+Shift+UType ff03, then Enter or Space.
HTML
＃CSS
\FF03Japanese IME
In a Japanese input method (IME), select fullwidth punctuation (zenkaku), then enter the sign; keystrokes vary by keyboard layout.
Codes and encoding1 code points
HTML decimal
＃
HTML hex
＃
CSS content
content: "\FF03";
Each escape is closed by the next backslash; a trailing space is needed before a literal hex digit.
URL encoded
%EF%BC%83
1
On screen
1
Code points
1
JS .length
3
UTF-8 bytes
A visible symbol can contain several code points. JS .length counts UTF-16 units; UTF-8 counts bytes.