Title: International Chemical Identifier
Long Title: IUPAC Gold Book - International Chemical Identifier
DOI: 10.1351/goldbook.11456
Status: current

Definition
A non-proprietary canonical identifier of chemical substances that can be used in printed and electronic data sources to enable easier linking of diverse data
 compilations.

Examples
1) Chloroacetic acid, "InChI=1/C2H3ClO2/c3-1-2(4)5/h1H2,(H,4,5)/p-1".
2) 2-Methylpyridine, "InChI=1S/C6H7N/c1-6-4-2-3-5-7-6/h2-5H,1H3".

Source
- PAC, 2016, 88, 239. 'Glossary of terms used in computational drug design, part II (IUPAC Recommendations 2015)' on page 248 (https://doi.org/10.1515/pac-2012-1204)

Other Outputs
- html: https://goldbook.iupac.org/terms/view/11456/html
- json: https://goldbook.iupac.org/terms/view/11456/json
- xml: https://goldbook.iupac.org/terms/view/11456/xml

Citation: Citation: 'International Chemical Identifier' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. 10.1351/goldbook.11456
License: The IUPAC Gold Book is licensed under Creative Commons Attribution-ShareAlike CC BY-SA 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/) for individual terms.
Collection: If you are interested in licensing the Gold Book for commercial use, please contact the IUPAC Executive Director at executivedirector@iupac.org .
Disclaimer: The International Union of Pure and Applied Chemistry (IUPAC) is continuously reviewing and, where needed, updating terms in the Compendium of Chemical Terminology (the IUPAC Gold Book). Users of these terms are encouraged to include the version of a term with its use and to check regularly for updates to term definitions that you are using.
Accessed: 2026-05-15T02:48:33+00:00