For round-trip compatibility with other encoding standards, Unicode has encoded many entities that are really variants of existing nominal characters. For example, the compatibility character ½ (U+00BD) corresponds to the nominal sequence 1/2 (U+0031, U+2044, and U+0032). Another example of compatibility equivalence is between circled and un-circled versions of characters.

Typically, compatibility characters differ in appearance from their nominal counterparts. Therefore, replacing a character by a compatibility equivalent may result in the lose of formatting information unless supplemented by markup or styling.