What � means
It stands in for text a conversion could not preserve. If your question mark in a box is stored as �, changing fonts cannot restore it. Recovery requires the original data and the correct rules for reading it as text.
The idea predates Unicode: ASCII, an earlier character-encoding system, had a substitute control character called SUB. RFC 20, a technical specification from 1969, describes its use for erroneous characters.
Treat unexpected � as a technical warning, not an emotional signal.
Do not infer the missing character from this mark.
Don't confuse it with
1/ .notdef replacement character vs missing glyph: � is stored text; .notdef names a font's fallback drawing when it cannot display a character. The underlying text may still be intact.
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.
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10
How to type or find �
- Search it as
- diamond question mark · question mark in a box · notdef
- Shows up in
- Anything that takes text · its shape is whatever your font draws
�\FFFDCodes and encoding1 code points
A visible symbol can contain several code points. JS .length counts UTF-16 units; UTF-8 counts bytes.