ISfinder is a specialized database for bacterial insertion sequences (ISs), serving as a reference center for these mobile genetic elements. It replaces the Stanford reference center and provides a centralized resource for naming, classification, and annotation of ISs. The database includes detailed information on each IS, such as DNA sequences, open reading frames, ends, target sites, origin, distribution, and family classification. It also offers extensive background information on ISs and transposons, along with online tools like BLAST for sequence analysis. ISfinder is used for annotating IS content in bacterial genomes and is recommended by several microbiology journals for registering new IS elements before publication. ISfinder categorizes ISs into families based on genetic organization, transposase similarity, and inverted repeats. It provides a coherent nomenclature system, similar to restriction enzymes, to avoid confusion. The database allows users to submit new IS sequences, which are then verified and added to the public database. It also includes a section on bacterial genomes, linking them to relevant information and providing details on IS content. ISfinder is continuously updated and expanded, with plans to add features like alignment tools and HMM profiles. It interacts with other databases, such as ACLAME, for comprehensive analysis of mobile genetic elements. The database is maintained by researchers at the CNRS and supported by various funding sources. ISfinder serves as a research tool for understanding the role of ISs in genome structure, distribution, and evolution.ISfinder is a specialized database for bacterial insertion sequences (ISs), serving as a reference center for these mobile genetic elements. It replaces the Stanford reference center and provides a centralized resource for naming, classification, and annotation of ISs. The database includes detailed information on each IS, such as DNA sequences, open reading frames, ends, target sites, origin, distribution, and family classification. It also offers extensive background information on ISs and transposons, along with online tools like BLAST for sequence analysis. ISfinder is used for annotating IS content in bacterial genomes and is recommended by several microbiology journals for registering new IS elements before publication. ISfinder categorizes ISs into families based on genetic organization, transposase similarity, and inverted repeats. It provides a coherent nomenclature system, similar to restriction enzymes, to avoid confusion. The database allows users to submit new IS sequences, which are then verified and added to the public database. It also includes a section on bacterial genomes, linking them to relevant information and providing details on IS content. ISfinder is continuously updated and expanded, with plans to add features like alignment tools and HMM profiles. It interacts with other databases, such as ACLAME, for comprehensive analysis of mobile genetic elements. The database is maintained by researchers at the CNRS and supported by various funding sources. ISfinder serves as a research tool for understanding the role of ISs in genome structure, distribution, and evolution.