Welcome to InChI


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.

Laboratory Information Systems

InChIKeys 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.

Identifier for Corporate Chemical Registries

InChIKeys are often used as the primary chemical identifier to create a chemical inventory for single site. Additionally InChIKeys are being used for complex inventories spanning multiple sites and research laboratories.

Integrating – 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 and Other Tools

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 related 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 InChI related resources to assist practicing scientists and educators in learning about and benefiting from the use of InChI.

Directions 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).

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 majority of the work on the InChI Standard is defining and coding enhancements and revisions of the InChI code base. This effort and the resulting code is donated to the InChI Trust by a broad community of developers and users. The Trust also maintains the open-source code repository and oversees the testing of changes and additions. The Trust also organizes frequent InChI community discussion groups to consider potential changes and suggest new directions for the InChI Standard.

The actual design and development of the various tools and capabilities that comprise the InChI code are done by the InChI Working Groups which are made up of staff from the InChI community. 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 work on the InChI code itself is contributed as fully open-source code to the project.

Latest InChI News (view all InChI news)

Catch up on progress and plans for InChI (April 21, 2024)

We held an online update on InChI on 26th March, covering current status and future roadmap for the standard:

Technical Update
InChI Subcommittee / Working Group Update
InChI Trust Organisational Update

View the recording: (Passcode: 2%9QJ%+y)


InChI Project Update for 2024 (January 7, 2024)

In 2021-2023, the InChI Trust decided to significantly invest in creating additional roles for outreach and technical direction – spending from our reserves to accelerate InChI development and transition this to a more open and transparent model. This was followed by the sad passing of Igor Pletnev, our primary developer, in late 2021.

Since then, much progress has been made transitioning the existing code to a GitHub environment, developing additional understanding of the code, fixing bugs and creating testing protocols that build on previous practice. This work has taken place at RWTH Aachen, supported by the NFDI4Chem project and the Volkswagen Foundation. The next ‘new’ version of InChI – rebuilding of the current version 1.06, cleaned-up and with additional bugfixes, is in testing and will be available for the IUPAC InChI Subcommittee and CPCDS to approve soon. The code now lives on GitHub – we are also working through the governance needed for this new development model aligned with IUPAC.

In parallel, much has been achieved by the Working Groups and the IUPAC InChI Subcommittee in agreeing the scientific requirements for extensions of the standard, and for implementation investigations to inform our technical roadmap.

The roadmap below covers both extensions to core InChI, and to InChI applications (RInChI, MInChI, the web demo and the resolver). Additional Working Groups are still considering their requirements.

In addition to the development resource at RWTH Aachen, we will also be supported by cheminformatics expertise from a new position at the Beilstein Institute. The InChI Trust is very grateful for this in-kind support from these organisations, and partnerships such as these are a fantastic way to achieve step-changes in speed of delivery, building on the core financial support from the Trust’s members, and input from IUPAC’s expert volunteers.

Having drawn on our reserves to catalyse these activities, the Trust now needs to reduce its annual spend so this is covered by core revenue. Given the focus on the technical roadmap for 2024-2025, we have prioritised our support towards technical oversight, coordination and planning. As a result we are reducing the support for roles in other areas. This refocus will enable us to deliver enhancements to InChI that have been long desired by our user community and grow partnerships and member contributions that will support further scientific activities to push the standard forward.

schematic of the InChI development roadmap for 2024-2025

Beilstein Institute Announces InChI Focused Job Opening (September 6, 2023)

The Beilstein Institute is looking to extend their current portfolio of open science projects by collaborating with the InChI Trust and they have created a new position at the Beilstein Institute focused on InChI. This is a unique opportunity to directly contribute to an international project by working in conjunction with the InChI community while contributing to the goals of a long-standing non-profit organization.
For more information go to https://www.beilstein-institut.de/en/about-us/jobs/

Deadline was November 15th 2023