InChI key

InChI key is a newer format of drug or chemical identification directly derived from InChI  and is always 27-characters long 1.  It is a non-proprietary identifier for chemical substances that can be used in printed and electronic data sources thus enabling easier linking of diverse data compilations 2.

The "key" format of the InChi key has several features that distinguish it from InChI and make it attractive for various purposes, including shorter text that allows for compact online searches and database linking 1.

DrugBank displays this information in the "Identification" section of the drug entry.  InChI and the InChI key are displayed adjacently, allowing the user to take note of the difference between the two identifiers  3.  As seen in the attached image 3, the InChI key for theobromine is much shorter and easier to read than the InChi 3. DrugBank imports InChI key information via ChemAxon.


  1. Heller SR, McNaught A, Pletnev I, Stein S, Tchekhovskoi D: InChI, the IUPAC International Chemical Identifier. J Cheminform. 2015 May 30;7:23. doi: 10.1186/s13321-015-0068-4. eCollection 2015. [Article]
  2. The IUPAC International Chemical Identifier [Link]
  3. Theobromine example, InChI and InChI key [File]