The CDK is an open-source Java software for cheminformatics and bioinformatics.

Key Features:
* Molecule and reaction valence bond representation.
* Read and write file formats: SMILES, SDF, InChI, Mol2, CML, and others.
* Efficient molecule processing algorithms: Ring Finding, Kekulisation, Aromaticity.
* Coordinate generation and rendering.
* Canonical identifiers for fast exact searching.
* Substructure and SMARTS pattern searching.
* ECFP, Daylight, MACCS, and other fingerprint methods for similarity searching.
* QSAR descriptor calculations

WWW: https://cdk.github.io/