CRISPRFinder is a web-based tool designed to identify clustered regularly interspaced short palindromic repeats (CRISPRs) in genomic sequences. CRISPRs are a family of tandem repeats found in prokaryotic genomes, consisting of highly conserved regions (DRs) and unique sequences called spacers. The tool offers several functionalities, including detecting CRISPRs, defining DRs, extracting spacers, obtaining flanking sequences, blasting spacers against databases, and checking for the presence of DRs in other sequenced genomes. CRISPRFinder is freely accessible at http://crispr.u-psud.fr/Server/CRISPRfinder.php. The software was developed in Perl under Debian Linux and can handle genomic sequences up to 67 Mb in length. It uses a suffix-tree-based algorithm to find maximal repeats and a scoring system to define DR consensus boundaries. The tool is user-friendly and provides detailed output, including a table of confirmed and questionable CRISPRs, a summary of CRISPR properties, and a fasta file of spacers. CRISPRFinder is particularly useful for identifying short CRISPR-like structures and for analyzing the evolution and distribution of CRISPRs.CRISPRFinder is a web-based tool designed to identify clustered regularly interspaced short palindromic repeats (CRISPRs) in genomic sequences. CRISPRs are a family of tandem repeats found in prokaryotic genomes, consisting of highly conserved regions (DRs) and unique sequences called spacers. The tool offers several functionalities, including detecting CRISPRs, defining DRs, extracting spacers, obtaining flanking sequences, blasting spacers against databases, and checking for the presence of DRs in other sequenced genomes. CRISPRFinder is freely accessible at http://crispr.u-psud.fr/Server/CRISPRfinder.php. The software was developed in Perl under Debian Linux and can handle genomic sequences up to 67 Mb in length. It uses a suffix-tree-based algorithm to find maximal repeats and a scoring system to define DR consensus boundaries. The tool is user-friendly and provides detailed output, including a table of confirmed and questionable CRISPRs, a summary of CRISPR properties, and a fasta file of spacers. CRISPRFinder is particularly useful for identifying short CRISPR-like structures and for analyzing the evolution and distribution of CRISPRs.