UniProt Archive (UniParc) is the most comprehensive, non-redundant protein sequence database available. Its protein sequences are retrieved from predominant, publicly accessible resources. To avoid redundancy, each unique sequence is stored only once with a stable protein identifier. As a result, performing a sequence search against UniParc is equivalent to performing the same search against all databases cross-referenced by UniParc.

UniProt Reference Clusters (UniRef) provides clustered sets of sequences from the UniProt Knowledgebase (UniProtKB) and selected UniParc records to obtain complete coverage of sequence space at several resolutions while hiding redundant sequences. The reduced redundancy increases the speed of similarity searches and improves detection of distant relationships.