The ChemSpider APIs enables developers to work with ChemSpider's database of chemical structures, properties, and associated information. There are two versions of this API: one RESTful and one SOAP-RPC. The REST API is replacing ChemSpider's legacy SOAP API. The new API comes with improvements to endpoint structure, payload validation, error handling, security, and developer support materials.
ChemSpider is a free chemical structure database that provides search access to more than 67 million structures from hundreds of data sources.