What ⁑ means
It is one character showing two vertically stacked asterisks.
The 2013 TeX proposal places it after * and before † in a footnote sequence. That is a typesetting suggestion, not a universal publishing rule.
Specialist and typographic; it reads as deliberate in carefully composed text.
Don't confuse it with
2*
Asterisk
An ordinary asterisk is one mark; ⁑ shows a pair arranged vertically.
**
Two asterisks side by side are two characters; ⁑ is one character with the marks stacked vertically.
Questions 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 2051, 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 “two asterisks aligned vertically”.
Linux
Ctrl+Shift+UType 2051, then Enter or Space.
HTML
⁑CSS
\2051LaTeX and PDF text extraction
In LaTeX, a macro can overlay two * characters to draw the shape. For extracted PDF text to contain ⁑ as one character, set its ActualText mapping to 2051.
Codes and encoding1 code points
HTML decimal
⁑
HTML hex
⁑
CSS content
content: "\2051";
Each escape is closed by the next backslash; a trailing space is needed before a literal hex digit.
URL encoded
%E2%81%91
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.