This disclosure relates to compressing and/or decompressing a group of similar data units, such as a table or queue of data units processed by a networking device or other computing apparatus. Each data unit in the group may only have values for fields in a master set. The described systems are particularly suited for hardware-level processing of groups of sparsely-populated data units, in which a large number of the data units have values for only a small number of the fields. In an embodiment, non-value carrying fields in a data unit are compressed based on a compression profile selected for the data unit. The compression profile indicates, for each master field, whether the compressed data unit includes a value for that field. Non-value carrying fields are omitted from the compressed data unit. The compression profile also permits compression of value-carrying fields using variable-width field lengths specified in the profile.