What ⦝ means
It marks the corner as exactly 90°. The dot sits inside the arc; this is a diagram mark, not an operation.
A 2011 geometry handbook documents the German right-angle symbol as an alternative in German-speaking countries and Poland.
The arc appears in Plato of Tivoli’s mid-12th-century translation of Savasorda’s geometry text Liber embadorum.
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 299D, 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 “measured right angle with dot”.
Linux
Ctrl+Shift+UType 299d, then Enter or Space.
HTML
⦝CSS
\299DUnicode input
Enter U+299D in an editor’s Unicode hex input; otherwise use its character map. A box means the font lacks the glyph.
Codes and encoding1 code points
HTML decimal
⦝
HTML hex
⦝
CSS content
content: "\299D";
Each escape is closed by the next backslash; a trailing space is needed before a literal hex digit.
URL encoded
%E2%A6%9D
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.