Welcome to InChI


The International Chemical Identifier

InChI is a structure-based chemical identifier, originally developed by IUPAC. As a standard identifier for chemical databases, InChI is essential for enabling effective information management across chemistry.

InChI with InChIKey are non-proprietary open standards. InChI turns chemical structures into unique machine readable strings, used for describing, storing and searching chemical structures. All associated algorithms and software are open source.

What is InChI and InChI KEY?

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 that is strictly unique, non-proprietary, open-source and is freely accessible.

InChIKey is a hashed version of InChI which allows for a compact representation and for searching in standard search engines like Google.

About the InChI Trust

The InChI Trust was created in May 2009 to provide continuing development and maintenance of the InChI Standard with contributions from a number of sources including InChI Members and the user community. The InChI Trust Board of Directors is comprised of a representative from each Member plus one member from the IUPAC InChI Subcommittee. The Board can add additional members as needed.

The InChI Trust Board and Project Director review requests for changes or extensions to the InChI Standard, define corresponding requirements and communicate these requirements to the InChI Trust with suggestions for prioritization. The Trust makes arrangements for the work needed to implement accepted changes to identify and secure sources of funding prior to any work starting.

Every release of InChI/InChIKey or related software requires IUPAC Subcommittee and InChI Trust approval before release. New versions of InChI/InChIKey and related standard software will be available on the InChI Trust website.

All releases of InChI algorithm will be on behalf the InChI Trust and will continue to be made available under an open-source license as mutually agreed between IUPAC and the InChI Trust.

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!

Laboratory Information Systems

InChI keys are used to integrate chemical data across other types of data in a research laboratory. This can include safety information, chemical properties, inventory, disposal, toxicity, etc.

Corporate Inventory Systems

InChI keys can be used to create a corporate chemicals inventory spanning multiple sites and research laboratories.

Chemical and Biological Data

Integrating chemical and biological databases is a critical operation for many organizations. InChIKeys can be used to provide the link between databases which contain information on chemicals as well as biological and many other types of data.

Search InChIKey in Google

Google has implemented the use of InChIKey for queries. An InChIKey can simply be embedded in a Google query to find all of the information on a chemical. This includes most patents and a broad set of additional chemical data.

InChI in Education (OER)

The InChI Open Education Resource (OER) is devoted to the use of InChI. Chemical nomenclature underpins chemical communication and InChI supports the advancement of chemical nomenclature into the digital age. InChI is evolving to handle reactions, mixtures and other needs of 21st century scientific communication, and yet there is little educational material available on the use of InChI.  OER provides resources to assist scientists and educators in learning about and benefiting from the use of InChI.

Direction and Priorities

The InChI Membership Program provides direction and priorities for the project. The code is maintained by a broad group of supporters from industry, government and academia and is contributed to the InChI Trust. There are about a dozen Working Groups extending InChI in many different areas of chemistry (nanomolecules, polymers, organometallics, Markush, etc.). We also support some paid software development for integrations across areas (like stereochemistry or tautomers).

Latest InChI News (view all InChI news)

November 7, 2022: Planning a Full InChI Projects Review at Fall ACS 2023 in San Francisco

  • We are planning a full day review of all of the active InChI projects at the Fall 2023 ACS meeting in San Francisco. The InChI Review will take place on Saturday Aug 12, 2023. The location in San Francisco will be finalized on the coming weeks. It will be a hybrid meeting with remote participation.

    Each active Working Group will provide an update and an overview of future plans.

August 25, 2022: InChI in the Wild: Celebrating Over 20 years of InChI Development in Memory of InChI Developer Igor Pletnev

  • This symposium honoring the many contributions of Igor Pletnev to the InChI project was held as part of the ACS Chicago 2022 meeting on Sunday August 21. Also covered were many research and development efforts to extend the InChI standard into additional areas of chemistry. The slide decks for these presentations are now available here.

July 1, 2022: Research Assistant/Associate - Software Development Position Open

  • Professor Dr. Sonja Herres-Pawlis, Institute of Inorganic Chemistry at RWTH Aachen University, has announced an open Reseach Assisstant position. The work will include further development of the IUPAC International Chemical Identifier (InChI), documentation of the programming developments and testing of extensions. The research group investigates topics in bioinorganic chemistry, sustainable polymerization catalysis, coordination chemistry and catalytic applications.

    Positions have been filled.

Our newsletter, InChI OUTREACH, will be published on a regular basis, once a quarter.  We will include the latest news, topics of interest, discussions on various aspects of InChI.  To view and download the the latest issue click here.