UTF-32 is the Unicode Transformation Format, or a method of encoding Unicode.

It was originally a subset of the UCS-4 standard. But the Principles and Procedures document of JTC1/SC2/WG2 states that all future assignments of characters will be constrained to the BMP for the first 14 supplementary planes and has removed former provisions for private-use code positions in groups 60 to 7F and in planes E0 to FF.

Accordingly UCS-4 and UTF-32 can be now taken to be identical save that UTF-32 standard has additional Unicode semantics that must be observed.