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SMILES to Structure — paste a SMILES, get an editable structure

Paste a SMILES string and get a clean, editable 2D chemical structure in your browser. Edit it, then copy a canonical SMILES, InChI, or InChIKey, or export MOL, SDF, PNG, or SVG. Free, no sign-up.

Try an example:

Best on a larger screen — editing is limited on phones. You can still view and copy identifiers.

Loading the structure editor…

Depiction auto-generated from the connectivity you pasted — not the original drawing. Use Clean up to re-lay-out.

This tool runs entirely in your browser. Your structures are never sent to a server.

Worked example: aspirin

Aspirin is CC(=O)Oc1ccccc1C(=O)O in SMILES. Paste it and the tool lays out a clean depiction of the acetyl group, the aromatic ring, and the carboxylic acid — connectivity preserved exactly as written. From there you can edit an atom or bond and copy the corrected canonical SMILES or InChIKey straight back out.

Frequently asked questions

Why won’t my SMILES parse?
The most common causes are a lowercase aromatic nitrogen that needs an explicit hydrogen — pyrrole written c1cccc1 has to be c1cc[nH]c1, the [nH] form — a ring the engine can’t kekulize into alternating single and double bonds, a valence that’s impossible for the element as written, or an unclosed or duplicated ring-closure digit. This tool reports the specific class and, where the fix is unambiguous (the [nH] case), offers a one-click correction instead of a blank canvas.
What identifiers can I get from a structure?
After the structure renders you can copy its SMILES, a canonical SMILES computed by RDKit, its InChI, and its InChIKey. The canonical form is the one to use when you’re comparing two structures for identity, because two different SMILES for the same molecule canonicalize to the same string.
SMILES vs InChI vs InChIKey vs MOL — which should I use when?
Use a SMILES when you want a short, human-readable string to paste into a paper, spreadsheet, or chat — but remember a plain SMILES is not unique, so use the canonical SMILES when you need to compare two molecules for identity. Use an InChI when you want a standard, vendor-neutral identifier that two different programs will agree on. Use an InChIKey — the fixed-length hash of the InChI — as a database and web-search key (it is what you Google or look up in PubChem), not as something you can decode back into a structure. Use a MOL or SDF file when you need to carry explicit 2D/3D coordinates, atom maps, or stereo wedges, or when a downstream tool expects an atom-block file rather than a line notation; SDF additionally bundles several records plus data fields in one file. This tool reads SMILES, InChI, and MOL/SDF and exports MOL, SDF, PNG, and SVG, so you can move a structure between any of these forms.
Is the depiction the same as my original drawing?
The 2D layout is generated from the connectivity you pasted, not from any coordinates in your input — so it may look different from a figure you copied out of a paper, even though the molecule is identical. The tool discloses involuntary changes it makes just to render (perceiving aromaticity, kekulizing for display); your connectivity is unchanged.
Can I turn an InChIKey back into a structure?
No. An InChIKey is a hashed fingerprint — a one-way function — so it can’t be decoded back into a structure. If you have an InChIKey, search for it on PubChem to find the compound and its full structure.
Does this work offline / is my structure private?
Everything runs in your browser. The parsing, layout, and identifier computation all happen client-side, so your structures are never uploaded to a server — safe for proprietary or unpublished compounds.

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