InChIKey to SMILES Converter
In short: Resolve InChIKey identifiers to canonical SMILES strings. It is free, works in your web browser and needs no download.
Resolve InChIKey identifiers to canonical SMILES using PubChem PUG REST.
Input and output formats
| Input: InChIKey | Output: SMILES | |
|---|---|---|
| Full name | InChIKey | SMILES (Simplified Molecular Input Line Entry System) |
| What it holds | A 27 character hash of the InChI, made for web and database search. It cannot be turned back into a structure without a lookup database. | Atoms, bonds, rings, charges and stereo as one line of text. No coordinates. |
| File or form | Text like XXXXXXXXXXXXXX-YYYYYYYYYY-Z | .smi or plain text |
File Format Explained
InChIKey is a compact hashed chemical identifier often used for database lookup and web search. It is not an editable structural notation by itself.
SMILES is an editable one-line structure string. This converter uses the InChIKey to find a matching compound record and then returns a SMILES representation.
Because InChIKey lookup depends on database records, unusual salts, mixtures, stereoisomers, or unmatched compounds may not resolve cleanly.
Why look up SMILES from an InChIKey
InChIKeys appear in many databases, patents, and supplementary files because they are short and searchable. To draw or modify the compound, you need a structure format; SMILES is the most convenient. This tool finds the record that matches the key and returns its SMILES.
How to use it
- Paste the full InChIKey, for example
BSYNRYMUTXBXSQ-UHFFFAOYSA-Nfor aspirin. - Convert to get the SMILES, here
CC(=O)OC1=CC=CC=C1C(=O)O. - Paste the SMILES into MolDraw or SMILES to Structure to view it.
FAQ
Why is the lookup sometimes empty? The key must exist in a public database. Keys for unpublished or proprietary compounds will not resolve. Does the last letter matter? Yes. It records protonation state, so a neutral acid and its deprotonated form have different keys. What about stereoisomers? Enantiomers share the first 14 characters but differ in the second block, so use the complete key to get the correct isomer.
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