ChemSpider is a free chemical database, owned by the Royal Society of Chemistry.

The database contains more than 26 million unique molecules from over 400 data sources including those listed below.

The ChemSpider database can be updated with user contributions including chemical structure deposition, spectra deposition and user curation. This is a crowdsourcing approach to develop an online chemistry database. Crowdsourced based curation of the data has produced a dictionary of chemical names associated with chemical structures that has been used in text-mining applications of the biomedical and chemical literature.

A number of available search modules are provided:

The ChemSpider database has been used in combination with text mining as the basis of chemistry document markup. ChemMantis, the Chemistry Markup And Nomenclature Transformation Integrated System uses algorithms to identify and extract chemical names from documents and web pages and converts the chemical names to chemical structures using name-to-structure conversion algorithms and dictionary look-ups in the ChemSpider database. The result is an integrated system between chemistry documents and information look-up via ChemSpider into over 150 data sources.