The International Chemical Identifier

InChI is a structure-based chemical identifier, developed by IUPAC and the InChI Trust. It is a standard identifier for chemical databases that facilitates effective information management across chemistry.

InChI and InChIKey are open standards. They use unique machine readable strings to represent, store and search chemical structures. All the software and algorithms related to them are open source.

What is InChI and InChIKey?

InChI identifiers describe chemical substances in terms of layers of information – the atoms and their bond connectivity, tautomeric information, isotope information, stereochemistry and electronic charge. The InChIKey is a fixed length (27 character) condensed digital representation of the InChI that is not designed to be human-understandable.

InChI is a structure-based identifier, strictly unique, and non-proprietary, open source and freely accessible.

InChIKey is a hashed version of InChI which allows for a compact representation and for searching.

Where are InChI and the InChIKey used?

InChI is used by most of the large chemical databases and software applications handling many millions of chemical structures.

InChI enables the linking and interlinking of chemistry and chemical structures on the web and computer platforms.  By enhancing the discoverability of chemical structures, InChI advances the ‘FAIR Guiding Principles for scientific data management and stewardship’. FAIR was published in 2016 to provide guidelines to improve the Findability, Accessibility, Interoperability, and Reuse of digital assets.  InChI provides ‘Findability’ for chemical structures and extends Interoperability between platforms, both of which foster Accessibility and Reuse.

The InChI Trust

The InChI Trust is a charity that supports the development and promotion of the InChI standard. It works in partnership with IUPAC to update and release new extensions to and applications of InChI. The Trust is a membership organisation, governed by its Board of Trustees which includes representation from IUPAC.

The scientific design of the various tools and capabilities that comprise the InChI code are defined by the InChI Working Groups which are made up of volunteers from the InChI community with IUPAC oversight. These voluntary groups are each focused on specific areas of chemistry or tools within the InChI code. See Working Groups for details on each group and their membership.

The development of the code is coordinated by the Technical Director of the InChI Trust, together with the working groups, IUPAC and our development partners. Our development partners currently include RWTH Aachen (as part of NFDI4Chem, acknowledging funding from Volkswagen Stiftung and the Data Literacy Alliance – DALIA), and the Beilstein-Institut.

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