IgBLAST is a web-based tool designed for the analysis of immunoglobulin (IG) variable domain sequences. It addresses the challenges of identifying and analyzing the germline V, D, and J genes, as well as the V-(D)-J junction details and FR/CDR boundaries, which are common tasks in IG sequence analysis. Unlike general-purpose tools like BLAST, IgBLAST is specifically tailored to handle the unique characteristics of IG sequences, such as their rearranged nature and variable gene lengths. The tool supports nucleotide and protein sequence analysis, batch processing, and simultaneous searches against germline gene databases and other sequence databases to minimize the chance of missing the best-matching germline V gene. IgBLAST provides detailed alignment views, tabulated summaries, and options for custom parameter adjustment, making it a robust and flexible tool for IG sequence analysis.IgBLAST is a web-based tool designed for the analysis of immunoglobulin (IG) variable domain sequences. It addresses the challenges of identifying and analyzing the germline V, D, and J genes, as well as the V-(D)-J junction details and FR/CDR boundaries, which are common tasks in IG sequence analysis. Unlike general-purpose tools like BLAST, IgBLAST is specifically tailored to handle the unique characteristics of IG sequences, such as their rearranged nature and variable gene lengths. The tool supports nucleotide and protein sequence analysis, batch processing, and simultaneous searches against germline gene databases and other sequence databases to minimize the chance of missing the best-matching germline V gene. IgBLAST provides detailed alignment views, tabulated summaries, and options for custom parameter adjustment, making it a robust and flexible tool for IG sequence analysis.