https://zinc.docking.org
No API key required. Fully open public API.
Resources follow a uniform pattern with format specified by file extension:
/{resource}.{format}
/{resource}/{id}.{format}
/{resource}/subsets/{subset}.{format}
Supported formats: .json, .csv, .txt, .smi, .sdf, .mol2, .xml, .png
Field selection (return only specific fields):
/{resource}.json:field1+field2+field3
GET /substances/ZINC000000000053.json
GET /substances.json?preferred_name=aspirin
GET /substances.json?inchikey=BSYNRYMUTXBXSQ-UHFFFAOYSA-N
GET /substances.json?mol_formula=C9H8O4
GET /substances.json?sub_id-matches=c1ccccc1&count=10
GET /substances.json?sub_id-matches-sma=[ND1]&count=10
The threshold (e.g., 40 = 40%) is part of the parameter name. Value can be SMILES or a ZINC ID number.
GET /substances/?ecfp4_fp-tanimoto-40=c1ccccc1O
GET /substances/?ecfp4_fp-tanimoto-70=ZINC000000000053
Filter by purchasability, drug status, reactivity, or origin:
GET /substances/subsets/fda.json # FDA-approved drugs
GET /substances/subsets/in-stock.json # In-stock compounds
GET /substances/subsets/metabolites.json # Metabolites
GET /substances/subsets/fda+in-stock.json # Combine subsets with +
Key subsets:
- Purchasability: in-stock, on-demand, for-sale, bb (building blocks)
- Drug status: fda, world, in-trials, in-man, in-vivo, in-vitro
- Origin: biogenic, metabolites, natural-products, endogenous
- Reactivity: anodyne, clean, standard, reactive
GET /genes/ACHE/substances.json?count=10
GET /catalogs.json # List all vendor catalogs
GET /catalogs/cmcd/substances.json # Substances in a catalog
GET /substances/ZINC000000000053.png
GET /apps/mol/convert?from=CC(=O)Oc1ccccc1C(=O)O&to=inchikey
Returns the InChIKey as plain text. Supports conversions between SMILES, InChI, and InChIKey.
Resolve multiple names, ZINC IDs, or SMILES at once:
POST /substances/resolved/
Content-Type: application/x-www-form-urlencoded
paste=aspirin%0Aibuprofen%0AZINC000000000053&identifiers=y&structures=y&names=y&output_format=json
count=N — results per page (use count=all cautiously on large sets)page=N — page number (1-indexed)sort=mwt — ascending by fieldsort=-mwt — descending (prefix with -)sort=no — disable sorting for faster bulk queriesmwt-le=500 — molecular weight <= 500logp-ge=2 — LogP >= 2hbd-le=5 — H-bond donors <= 5-le (<=), -ge (>=), -lt (<), -gt (>), -eq (=)Molecular properties: mwt, logp, hba, hbd, tpsa, rb (rotatable bonds), num_rings, num_aromatic_rings, num_heavy_atoms, num_chiral_centers, fractioncsp3
Identifiers: zinc_id, smiles, inchikey, mol_formula, preferred_name, cas_numbers
Status: purchasable, reactive, bb (building block)
GET /substances/ZINC000000000053.json:zinc_id+smiles+mwt+logp+hba+hbd+tpsa+mol_formula+preferred_name
GET /substances/subsets/fda.json:zinc_id+preferred_name+mwt?sort=mwt&count=10
GET /substances/subsets/for-sale.json?mwt-le=500&logp-le=5&hbd-le=5&hba-le=10&count=20
GET /genes/EGFR/substances.json:zinc_id+preferred_name+smiles?count=10
[
{
"zinc_id": "ZINC000000000053",
"smiles": "CC(=O)Oc1ccccc1C(=O)O",
"preferred_name": "aspirin",
"mwt": 180.159,
"logp": 1.31,
"hba": 3,
"hbd": 1,
"tpsa": 63,
"mol_formula": "C9H8O4",
"inchikey": "BSYNRYMUTXBXSQ-UHFFFAOYSA-N",
"purchasable": 5
}
]
Responses are JSON arrays. Single-record lookups (by ZINC ID) return a JSON object.
No documented rate limits. The API is publicly funded (NIH NIGMS GM71896). Be respectful:
- Use count= to limit result sizes
- Use sort=no for faster bulk queries
- Similarity and substructure searches are computationally expensive — expect slower responses
- Avoid count=all on large result sets
count= to limit resultsZINC000000000053 (15-digit zero-padded after "ZINC").smi format returns SMILES strings, useful for cheminformatics pipelines.sdf format returns 3D structures suitable for docking software+ (e.g., fda+in-stock = FDA-approved AND in-stock)/tranches/) to partition by molecular weight and LogP