Chemspider

ChemSpider is an extremely useful free, online chemical structure database maintained by the Royal Society of Chemistry (RSC) that provides access to over 130 million community submitted chemical structures along with associated properties, spectra, literature links and supplier information. 

Who it serves & how
ChemSpider serves chemists, materials scientists, biochemists, educators and students worldwide. It allows users to:

• Search for compounds by name, CAS number, molecular formula, or by drawing/sub-structure search. 
• Explore physicochemical properties (such as melting point, solubility, log P), spectral data (if available), supplier links and related literature. 
• Contribute by submitting new structures, spectra or curating existing records—opening a crowdsourced dimension to the database. 

For researchers anywhere working with small molecules, chemical inventories, or needing a reliable checking point for structure/property information, ChemSpider offers a one-stop, no-cost resource that can save time and enhance data quality.

Key features

• Large-scale: integration of data from hundreds of sources, offering breadth and depth of chemical coverage. 
• Structure and sub-structure search: users can draw a molecule, search for similar or related compounds, or query by formula ranges. 
• Free access and no mandatory subscription: the service is open to all, though some advanced features or bulk access may have constraints. 
• Downloads & linking: While full database dumps may have restrictions, key data links back to original sources, enabling traceability. 

Considerations & limitations

• Because ChemSpider aggregates from many sources, data completeness and quality may vary by compound—some entries will have rich information (spectra, properties), others only minimal.
• While structure search is powerful, for highly specialised or proprietary datasets (e.g., unpublished compounds, industrial inventories) you may still need commercial databases.
• Bulk downloads or API usage may require registration or adhere to usage terms, always check licensing for reuse.
• Coverage is heavily skewed toward small molecules, if your work is in large biomolecules, polymers or complex materials, you may need complementary resources.