What are Revit Omniclass Codes?

Assigning OmniClass codes

OmniClass is a new classification system for the construction industry. The Autodesk Seek web site uses codes from OmniClass Table 23 to filter and identify shared content. A code consists of an OmniClass number and title.

If an OmniClass code is not already assigned to a family, you are prompted to assign one during the sharing process. However, you can continue to share with Autodesk Seek without defining one. All Revit families (except the System and Annotation families) have parameters for assigning an OmniClass code.

You can access the OmniClass Number and OmniClass Title parameters in the Family Category and Parameters dialog under Family Parameters. See Family Category and Parameters.

Taken from here.