Compatibility equivalence refers to a state in which two technically dissimilar things may be considered functionally identical.

In Unicode, for instance, the compatibility equivalence of two strings (sequences of letters, numbers, or other characters) means that they can be reduced to identical strings by recursive application of both canonical decomposition and compatibility decomposition routines. (Compare this with canonical equivalence.)

Two Unicode strings that have the relation of compatibility equivalence may sometimes be considered identical, but generally they are not—the "micro sign" (µ) and "greek small letter mu" (μ) are similar, for example, but they are not considered strictly identical.