What are InChI and InChIKey?


What is an InChI?

The International Union of Pure and Applied Chemistry (IUPAC) developed the InChI (International Chemical Identifier") standard, a textual representation of chemical substances, to provide a standard way to encode molecular information and to facilitate the search for such information in databases and on the web.

InChI is made of layers. InChI can be seen as a barcode to uniquely identify chemical structures.


What is an InChIKey?

The condensed InChIKey is a hashed version of the full InChI (created using the SHA-256 algorithm). It was designed for easy web searches of chemical compounds.


An InChIKey can be used to quickly match identical structures or those that differ only in charge or stereochemistry.