The UniProt Consortium, consisting of the European Bioinformatics Institute (EBI), the Swiss Institute of Bioinformatics (SIB), and the Protein Information Resource (PIR), maintains the UniProt database. UniProt provides a comprehensive, well-annotated protein sequence knowledgebase with extensive cross-references and querying interfaces. It includes four main components: the UniProt Archive (UniParc), the UniProt Knowledgebase (UniProtKB), the UniProt Reference Clusters (UniRef), and the UniProt Metagenomic and Environmental Sequences database (UniMES). UniProt is updated every three weeks and is freely accessible online. UniProtKB contains two sections: UniProtKB/Swiss-Prot, which contains manually annotated records with detailed information, and UniProtKB/TrEMBL, which contains computationally annotated records. UniRef clusters sequences based on identity to reduce redundancy and improve search efficiency. UniParc is a comprehensive sequence repository that includes all protein sequences from public sources. UniMES is a database for metagenomic sequences, providing access to genomic data from environmental samples. UniProtKB/Swiss-Prot provides detailed annotations for proteins from model organisms, including humans, mammals, non-mammalian vertebrates, bacteria, plants, fungi, viruses, and others. Annotations include functional information, post-translational modifications, subcellular localization, and interactions. UniProt also includes controlled vocabularies for describing annotations, such as those for plastids and metabolic pathways. UniProt has been updated to include more than 105,000 distinct proteins with detailed annotations. The database is integrated with other resources, including the ENZYME database and KEGG for metabolic pathway information. UniProt provides tools for searching, downloading, and analyzing protein data, and is freely available for both commercial and non-commercial use. Feedback is encouraged to improve the database and its services. Funding comes from various sources, including the National Human Genome Research Institute and the European Commission.The UniProt Consortium, consisting of the European Bioinformatics Institute (EBI), the Swiss Institute of Bioinformatics (SIB), and the Protein Information Resource (PIR), maintains the UniProt database. UniProt provides a comprehensive, well-annotated protein sequence knowledgebase with extensive cross-references and querying interfaces. It includes four main components: the UniProt Archive (UniParc), the UniProt Knowledgebase (UniProtKB), the UniProt Reference Clusters (UniRef), and the UniProt Metagenomic and Environmental Sequences database (UniMES). UniProt is updated every three weeks and is freely accessible online. UniProtKB contains two sections: UniProtKB/Swiss-Prot, which contains manually annotated records with detailed information, and UniProtKB/TrEMBL, which contains computationally annotated records. UniRef clusters sequences based on identity to reduce redundancy and improve search efficiency. UniParc is a comprehensive sequence repository that includes all protein sequences from public sources. UniMES is a database for metagenomic sequences, providing access to genomic data from environmental samples. UniProtKB/Swiss-Prot provides detailed annotations for proteins from model organisms, including humans, mammals, non-mammalian vertebrates, bacteria, plants, fungi, viruses, and others. Annotations include functional information, post-translational modifications, subcellular localization, and interactions. UniProt also includes controlled vocabularies for describing annotations, such as those for plastids and metabolic pathways. UniProt has been updated to include more than 105,000 distinct proteins with detailed annotations. The database is integrated with other resources, including the ENZYME database and KEGG for metabolic pathway information. UniProt provides tools for searching, downloading, and analyzing protein data, and is freely available for both commercial and non-commercial use. Feedback is encouraged to improve the database and its services. Funding comes from various sources, including the National Human Genome Research Institute and the European Commission.