The article introduces CASTp 3.0, an updated version of the Computed Atlas of Surface Topography of proteins web server. CASTp 3.0 continues to provide reliable and comprehensive identification and quantification of protein topographic features, including surface pockets, interior cavities, and cross channels. New features include imprints of negative volumes of these features, pre-computed topographic data for biological assemblies in the Protein Data Bank (PDB), improved visualization tools, and enhanced user interface. The server uses the alpha shape method to identify and measure these features and offers detailed information on secondary structures, functional sites, and variant sites. The CASTp 3.0 server is freely accessible and has been widely used in various studies, including drug discovery and protein function analysis.The article introduces CASTp 3.0, an updated version of the Computed Atlas of Surface Topography of proteins web server. CASTp 3.0 continues to provide reliable and comprehensive identification and quantification of protein topographic features, including surface pockets, interior cavities, and cross channels. New features include imprints of negative volumes of these features, pre-computed topographic data for biological assemblies in the Protein Data Bank (PDB), improved visualization tools, and enhanced user interface. The server uses the alpha shape method to identify and measure these features and offers detailed information on secondary structures, functional sites, and variant sites. The CASTp 3.0 server is freely accessible and has been widely used in various studies, including drug discovery and protein function analysis.