What ㏈ means
Yes: both denote the decibel unit. The square changes how the letters fit on the page, not what they measure.
Some East Asian character sets used fixed-width cells, giving each character one slot. Square forms let Latin abbreviations fit one slot beside Chinese and other East Asian characters. Unicode lists Japanese character-set standards JIS X 0208 and JIS X 0213 among sources for this repertoire.
Don't confuse it with
1dB
This is the ordinary two-letter unit symbol; ㏈ is its one-cell compatibility form, not a different unit.
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 33C8, 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 “square db”.
Linux
Ctrl+Shift+UType 33c8, then Enter or Space.
HTML
㏈CSS
\33C8Codes and encoding1 code points
HTML decimal
㏈
HTML hex
㏈
CSS content
content: "\33C8";
Each escape is closed by the next backslash; a trailing space is needed before a literal hex digit.
URL encoded
%E3%8F%88
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.