Many annotations in the GNPS library are only compound names without SMILES. This filter derives the canonical SMILES, InChI and InChIKey from PubChem. It will only add SMILES to the annotation if the mass found on PubChem matches with the parent mass in the metadata. Previously found compound names are stored in a file and reused. This significantly reduces the number of times a compound name has to be looked up. For cleaning new libraries these files with common compound names can also be reused.