Project Details IUPAC International Chemical Identifier (InChI): Promotion and Extension

Project No.:
Start Date:
01 January 2005
End Date:
31 January 2009


Following the launch of InChI version 1.0:

  • to promote its use throughout the chemical information community
  • to extend its applicability to include polymeric structures
  • to explore the need for other extensions, including the ability to handle Markush structures, and to include information on other attributes such as phases and excited states

> InChI version 1.0 release (Chem. Int. July 2005)


Version 1.0 of the Identifier expresses chemical structures in a standard machine-readable format, in terms of atomic connectivity, tautomeric state, isotopes, stereochemistry, and electronic charge. It deals with neutral and ionic well-defined, covalently-bonded organic molecules, and also with inorganic, organometallic and coordination compounds.

We propose to promote actively the use of the algorithm and its associated implementations to developers of commercial chemical software, database compilers and publishers of chemical information, in order to enable sharing of molecular information throughout the worldwide community of chemical scientists.

We propose also to extend the applicability of the Identifier to polymeric structures, and to explore the need for and the practicality of an extension to cover Markush structures.

In addition, we will evaluate the need for inclusion of information on other attributes such as phases and excited states, and take steps to include such information if appropriate.


This project was presented at a poster session at the IUPAC Congress/GA July 2005
>view pdf – 484KB<

Version 1 of IUPAC’s International Chemical Identifier (InChI) has been released in April 2005; software, documentation, source code and licensing conditions are available from the IUPAC website at

An InChI FAQ presented by Nick Day (Unilever Centre for Molecular Informatics, Cambridge University) is available from


May 2005 update
To enable development of InChI facilities and applications in an Open Source context, a project to encompass this work has been registered with (see; people wishing to participate should contact the project administrator ( or the IUPAC Secretariat ( To receive and discuss proposals for InChI enhancements, an internet listserver has also been established; people wishing to participate in these discussions should contact Alan McNaught (
This project was presented at a poster session at the IUPAC Congress/GA July 2005
>view pdf – 484KB<

June 2005 update
The project team met in Prague on June 3rd 2005 to consider extension to polymeric structures > notes of the meeting (pdf 15KB).

August 2006 update
InChI version 1 software version 1.01 has been released. See
This release includes the following new features:

  • InChI validation protocol to establish whether software that includes the InChI algorithm produces valid InChI
  • InChI reversal: InChI to structure conversion (connection table, bond orders, charges, stereochemical parities; the resultant structures have no coordinates; success rate on average 99.7%)
  • Several bug fixes that eliminate known InChI failures
  • Several minor additional features

For more details see Whats_New.pdf included in the package.

Q: Why is the InChI version in this package 1, not 1.01?
A: The version of the chemical identifier (as a string of characters derived from a chemical structure) is the same, only the software and documentation were updated. Therefore, the InChI version is still version 1.

> InChI1.0 release published in Chem. Int. July/Aug 2005

> InChI 1.01 release published in Chem. Int. Nov/Dec 2006 – see issue index

January 2009 update
InChI Software Version 1.02 final, implemented for Standard InChI/InChIKey has been released. See

See Chem. Int. Jan ’09, p. 7 for an article titled ‘The IUPAC International Chemical Identifier (InChI)‘, by Stephen R. Heller and Alan D. McNaught, and on the ‘Use of InChI and InChIKey in the XML Gold Book‘, by Bedrich Kosata

Feb 09 project completed – continuation as project 2008-033-1-800

last update 20090319