NAMS (Non-contiguous Atom Matching Structural Similarity) is a free Webtool to calculate similarity between molecules based on the structural/topological relationships of each atom towards all the others within a molecule. This functionality allows the calculation of similarity between 2 molecules using their name, SMILES or InChI and setting several parameters that will influence the atom/bond matching similarity score. Disconnected fragments will be separated in order to keep only the main structure and molecules with less than 3 atoms cannot be processed. It is also possible the calculation of different similarity functions based on Fingerprints.