The free chemistry database from the NIH.
At a Glance
| Publisher | NIH / NCBI |
| Coverage | 100M+ unique compounds and 300M+ substances, plus bioassay data, drawn from hundreds of data sources |
| Access | free; open API |
| Free alternative | it is the free option |
| Regional | global. |
Our Take
PubChem is the free backbone of open chemical information — compound and substance records, properties, and bioassay results, all openly available with a robust API that makes it a default data source for cheminformatics and drug-discovery pipelines. It doesn’t offer the curated reaction and retrosynthesis depth of SciFinder or Reaxys, but for identity, properties, and bioactivity at zero cost it’s outstanding. Use it as the free substance and bioassay reference and as a programmatic data source; step up to SciFinder/Reaxys for reaction-level work.
Power Tips
- Use the PubChem API to pull compound identifiers, properties, and bioassay data at scale for cheminformatics — free, no subscription
- start substance identity checks here before paying for a reaction database.
Alternatives & Complements
SciFinder (CAS) · Reaxys · ChemRxiv · Europe PMC.
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