U+FFFC OBJECT REPLACEMENT CHARACTER

U+FFFC was added to Unicode in version 2.1 (1998). It belongs to the block Specials in the Basic Multilingual Plane.

This character is a Other Symbol and is commonly used, that is, in no specific script.

The glyph is not a composition. It has a Neutral East Asian Width. In bidirectional context it acts as Other Neutral and is not mirrored. In text U+FFFC behaves as Contingent Break regarding line breaks. It has type Other for sentence and Other for word breaks. The Grapheme Cluster Break is Any.

The Wikipedia has the following information about this codepoint:

Specials is the name of a short Unicode block allocated at the very end of the Basic Multilingual Plane, at U+FFF0–FFFF. Of these 16 codepoints, 5 are assigned as of Unicode 7.0:

• U+FFF9 interlinear annotation anchor, marks start of annotated text
• U+FFFA interlinear annotation separator, marks start of annotating character(s)
• U+FFFB interlinear annotation terminator, marks end of annotation block
• U+FFFC  object replacement character, placeholder in the text for another unspecified object, for example in a compound document.
• U+FFFD � replacement character used to replace an unknown or unrepresentable character
• U+FFFE <noncharacter-FFFE> not a character.
• U+FFFF <noncharacter-FFFF> not a character.

FFFE and FFFF are not unassigned in the usual sense, but guaranteed not to be a Unicode character at all. They can be used to guess a text's encoding scheme, since any text containing these is by definition not a correctly encoded Unicode text. The U+FEFF is Unicode's byte-order mark, named "zero-width no-break space" (as inclusion of it in text shall not be noticed). If this character is read in the wrong byte order (for example, due to an endianness bug), it will read 0xFFFE, which is illegal Unicode.