Notdef glyph
Notdef glyph or .notdef is a special character that indicates that no visual representation (glyph) exists for a character (code point) in text data.
The name is a contraction of "not defined", and the word glyph from Ancient Greek, a graphical representation of a character or symbol. The name .notdef is due to names starting with a period being reserved for internal use by various font definition formats.
Usage
[edit]Text rendering uses the notdef glyph when no glyph is available in the current (computer) font or any fallback font.[1] As there are many code points that Unicode has not even assigned appearances to, usage of .notdef is unavoidable.[2]
Before the use of fallback fonts the glyph was very common, and fixing the display involved changing the current font to one designed for the language of the source text. Nowadays it is most often encountered replacing emoji sent between systems, because one or other of iOS or Android add a Unicode emoji before the other does.[3] It is also seen when Private Use Areas are used, for example, a group studying an ancient or rare language may need to encode its graphemes: the group can share the grapheme-to-codepoint allocation that they have agreed but readers who do have that information will see only .notdef symbols. It is also seen in quotes and apostrophes from CP1252 text that has been mis-translated to UTF-8.
Representations
[edit]The font chooses the appearance of the notdef glyph, it can vary depending on the font. Frequently observed forms include:[citation needed]
- An empty rectangle, often called a tofu.
- The empty rectangle with a question mark, cross, or other glyph inside it
- A square with the Unicode code point written in hex.[citation needed]
- This browser and font displays .
The notdef glyph should not be confused with U+FFFD � REPLACEMENT CHARACTER which is used to indicate encoding errors, which are not code points.
See also
[edit]- Character encoding – Using numbers to represent text characters
- Font – Particular size, weight and style of a typeface
- Typeface – Set of characters that share common design features
- Typographic symbol
- Unicode – Character encoding standard
References
[edit]- ↑ Microsoft (2022-06-09). "Recommendations for OpenType Fonts (OpenType 1.7) - Typography". learn.microsoft.com. Retrieved 2024-01-06.
- ↑ "Missing characters and glyphs". W3C. Retrieved 2025-06-22.
- ↑ "Why are Some Emojis Not Showing Up? Here's How to Fix Those Appearing in Boxes". TechTimes. 2020-07-24. Retrieved 2025-06-22.
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