The very notion of a SMILES standard may not be realistic at this point. Today a dozen or more slightly different implementations are in use. None of them can be considered a reference standard. Some have introduced extensions not recognized by the others, contributing to language drift while compounding the already formidable difficulties faced by implementors. Others claim SMILES compatibility while ignoring certain aspects of the documentation that does exist. The Daylight implementation, like some of the others, is distributed under a commercial license that restricts use , and a publicly-accessible web service operated for many years was decommissioned . Although SMILES may underpin a lot of modern chemical information exchange, the foundations of this system are weathered and showing signs of stress.