 Fifteen years have passed since the International Union of Pure and Applied Chemistry (IUPAC) international chemical identifier (InChI) project [1–8] was initiated in 2000. The increasing complexity of molecular structures was making conventional naming procedures inconvenient, and there was no suitable, openly available electronic format for linking chemical structures over the Internet. So, InChI was developed as a freely available, non-proprietary identifier for chemical substances that can be used in printed and electronic data sources, thus enabling easier linking of data compilations and unambiguous identification of chemical substances. It was developed under the auspices of IUPAC, with principal contributions from the US National Institute of Standards and Technology (NIST), and more recently, the InChI Trust [9]. The Trust is a not-for-profit organization that develops and improves on the current standard.