The Specials Unicode block, located at the end of the Basic Multilingual Plane from U+FFF0 to U+FFFF, includes code points such as U+FFF9 (INTERLINEAR ANNOTATION ANCHOR) marking the start of annotated text, U+FFFA and U+FFFB defining annotation boundaries, and U+FFFC, the OBJECT REPLACEMENT CHARACTER used as a placeholder in a compound document. U+FFFD is the REPLACEMENT CHARACTER for unknown or unrepresentable symbols. The final two, U+FFFE and U+FFFF, are noncharacters reserved but valid in Unicode. The CLDR algorithm uses U+FFFE internally, while U+FEFF ZERO WIDTH NO-BREAK SPACE signals text endianness. Originally named Special in Unicode 1.0, this block serves specialized text processing purposes.
Replacement character
The replacement character � (often displayed as a black rhombus with a white question mark) is a symbol found in the Unicode standard at code point U+FFFD in the Specials table. It is used to indicate problems when a system is unable to render a stream of data to correct symbols.4
As an example, a text file encoded in ISO 8859-1 containing the German word für contains the bytes 0x66 0xFC 0x72. If this file is opened with a text editor that assumes the input is UTF-8, the first and third bytes are valid UTF-8 encodings of ASCII, but the second byte (0xFC) is not valid in UTF-8. The text editor could replace this byte with the replacement character to produce a valid string of Unicode code points for display, so the user sees "f�r".
A poorly implemented text editor might write out the replacement character when the user saves the file; the data in the file will then become 0x66 0xEF 0xBF 0xBD 0x72. If the file is re-opened using ISO 8859-1, it will display "f�r" (this is called mojibake). Since the replacement is the same for all errors it is impossible to recover the original character.
At one time the replacement character was often used when there was no glyph available in a font for that character, as in font substitution. However, most modern text rendering systems instead use a font's .notdef character, which in most cases is an empty box, or "?" or "X" in a box5 (this browser displays ), sometimes called a 'tofu'. There is no Unicode code point for this symbol.
Thus the replacement character is now only seen for encoding errors. Some software programs translate invalid UTF-8 bytes to matching characters in Windows-1252 (since that is the most common source of these errors), so that the replacement character is never seen.
Unicode chart
| Specials[1][2][3]Official Unicode Consortium code chart (PDF) | ||||||||||||||||
| 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | A | B | C | D | E | F | |
| U+FFFx | IAA | IAS | IAT |  | � | |||||||||||
| Notes1.^ As of Unicode version 16.02.^ Grey areas indicate non-assigned code points3.^ Black areas indicate noncharacters (code points that are guaranteed never to be assigned as encoded characters in the Unicode Standard) | ||||||||||||||||
History
The following Unicode-related documents record the purpose and process of defining specific characters in the Specials block:
| Version | Final code points6 | Count | UTC ID | L2 ID | WG2 ID | Document |
|---|---|---|---|---|---|---|
| 1.0.0 | U+FFFD | 1 | (to be determined) | |||
| U+FFFE..FFFF | 2 | (to be determined) | ||||
| L2/01-295R | Moore, Lisa (2001-11-06), "Motion 88-M2", Minutes from the UTC/L2 meeting #88 | |||||
| L2/01-355 | N2369 (html, doc) | Davis, Mark (2001-09-26), Request to allow FFFF, FFFE in UTF-8 in the text of ISO/IEC 10646 | ||||
| L2/02-154 | N2403 | Umamaheswaran, V. S. (2002-04-22), "9.3 Allowing FFFF and FFFE in UTF-8", Draft minutes of WG 2 meeting 41, Hotel Phoenix, Singapore, 2001-10-15/19 | ||||
| 2.1 | U+FFFC | 1 | UTC/1995-056 | Sargent, Murray (1995-12-06), Recommendation to encode a WCH_EMBEDDING character | ||
| UTC/1996-002 | Aliprand, Joan; Hart, Edwin; Greenfield, Steve (1996-03-05), "Embedded Objects", UTC #67 Minutes | |||||
| N1365 | Sargent, Murray (1996-03-18), Proposal Summary – Object Replacement Character | |||||
| N1353 | Umamaheswaran, V. S.; Ksar, Mike (1996-06-25), "8.14", Draft minutes of WG2 Copenhagen Meeting # 30 | |||||
| L2/97-288 | N1603 | Umamaheswaran, V. S. (1997-10-24), "7.3", Unconfirmed Meeting Minutes, WG 2 Meeting # 33, Heraklion, Crete, Greece, 20 June – 4 July 1997 | ||||
| L2/98-004R | N1681 | Text of ISO 10646 – AMD 18 for PDAM registration and FPDAM ballot, 1997-12-22 | ||||
| L2/98-070 | Aliprand, Joan; Winkler, Arnold, "Additional comments regarding 2.1", Minutes of the joint UTC and L2 meeting from the meeting in Cupertino, February 25-27, 1998 | |||||
| L2/98-318 | N1894 | Revised text of 10646-1/FPDAM 18, AMENDMENT 18: Symbols and Others, 1998-10-22 | ||||
| 3.0 | U+FFF9..FFFB | 3 | L2/97-255R | Aliprand, Joan (1997-12-03), "3.D Proposal for In-Line Notation (ruby)", Approved Minutes – UTC #73 & L2 #170 joint meeting, Palo Alto, CA – August 4-5, 1997 | ||
| L2/98-055 | Freytag, Asmus (1998-02-22), Support for Implementing Inline and Interlinear Annotations | |||||
| L2/98-070 | Aliprand, Joan; Winkler, Arnold, "3.C.5. Support for implementing inline and interlinear annotations", Minutes of the joint UTC and L2 meeting from the meeting in Cupertino, February 25-27, 1998 | |||||
| L2/98-099 | N1727 | Freytag, Asmus (1998-03-18), Support for Implementing Interlinear Annotations as used in East Asian Typography | ||||
| L2/98-158 | Aliprand, Joan; Winkler, Arnold (1998-05-26), "Inline and Interlinear Annotations", Draft Minutes – UTC #76 & NCITS Subgroup L2 #173 joint meeting, Tredyffrin, Pennsylvania, April 20-22, 1998 | |||||
| L2/98-286 | N1703 | Umamaheswaran, V. S.; Ksar, Mike (1998-07-02), "8.14", Unconfirmed Meeting Minutes, WG 2 Meeting #34, Redmond, WA, USA; 1998-03-16--20 | ||||
| L2/98-270 | Hiura, Hideki; Kobayashi, Tatsuo (1998-07-29), Suggestion to the inline and interlinear annotation proposal | |||||
| L2/98-281R (pdf, html) | Aliprand, Joan (1998-07-31), "In-Line and Interlinear Annotation (III.C.1.c)", Unconfirmed Minutes – UTC #77 & NCITS Subgroup L2 # 174 JOINT MEETING, Redmond, WA -- July 29-31, 1998 | |||||
| L2/98-363 | N1861 | Sato, T. K. (1998-09-01), Ruby markers | ||||
| L2/98-372 | N1884R2 (pdf, doc) | Whistler, Ken; et al. (1998-09-22), Additional Characters for the UCS | ||||
| L2/98-416 | N1882.zip | Support for Implementing Interlinear Annotations, 1998-09-23 | ||||
| L2/98-329 | N1920 | Combined PDAM registration and consideration ballot on WD for ISO/IEC 10646-1/Amd. 30, AMENDMENT 30: Additional Latin and other characters, 1998-10-28 | ||||
| L2/98-421R | Suignard, Michel; Hiura, Hideki (1998-12-04), Notes concerning the PDAM 30 interlinear annotation characters | |||||
| L2/99-010 | N1903 (pdf, html, doc) | Umamaheswaran, V. S. (1998-12-30), "8.2.15", Minutes of WG 2 meeting 35, London, U.K.; 1998-09-21--25 | ||||
| L2/98-419 (pdf, doc) | Aliprand, Joan (1999-02-05), "Interlinear Annotation Characters", Approved Minutes -- UTC #78 & NCITS Subgroup L2 # 175 Joint Meeting, San Jose, CA -- December 1-4, 1998 | |||||
| UTC/1999-021 | Duerst, Martin; Bosak, Jon (1999-06-08), W3C XML CG statement on annotation characters | |||||
| L2/99-176R | Moore, Lisa (1999-11-04), "W3C Liaison Statement on Annotation Characters", Minutes from the joint UTC/L2 meeting in Seattle, June 8-10, 1999 | |||||
| L2/01-301 | Whistler, Ken (2001-08-01), "E. Indicated as "strongly discouraged" for plain text interchange", Analysis of Character Deprecation in the Unicode Standard | |||||
See also
References
"Corrigendum #9: Clarification About Noncharacters". The Unicode Standard. Archived from the original on Jun 10, 2023. Retrieved 2023-06-07. http://www.unicode.org/versions/corrigendum9.html ↩
"Unicode Technical Standard #35". Unicode Locale Data Markup Language (LDML). Retrieved 2024-08-27. http://www.unicode.org/reports/tr35/tr35-collation.html#Algorithm_FFFE ↩
"3.8: Block-by-Block Charts" (PDF). The Unicode Standard. Version 1.0. Unicode Consortium. Archived (PDF) from the original on 2021-02-11. Retrieved 2020-09-30. https://www.unicode.org/versions/Unicode1.0.0/CodeCharts2.pdf ↩
Wichary, Marcin (September 29, 2020). "When fonts fall". Figma. Archived from the original on 13 June 2021. Retrieved 6 June 2021. https://www.figma.com/blog/when-fonts-fall/ ↩
"Recommendations for OpenType Fonts (OpenType 1.7) - Typography". Microsoft Learn. Archived from the original on 19 October 2020. Retrieved 18 October 2020. https://docs.microsoft.com/en-us/typography/opentype/otspec170/recom#shape-of-notdef-glyph ↩
Proposed code points and characters names may differ from final code points and names ↩