A UID is a globally unique identifier consisting of a 32-bit number. UIDs are used throughout the Symbian platform to enable various kinds of file identification and association.

Because UIDs are fundamental to the Symbian platform, it is important that they are used correctly when developing programs. To ensure uniqueness, it is essential that UIDs are properly allocated. Uniqueness is guaranteed by allocating UIDs centrally from a database managed by Symbian at https://www.symbiansigned.com.