SMILES shrank a molecule to one ASCII string and became chemistry's shorthand

Before SMILES, chemists shared structures as connection tables or drawings, which were bulky and awkward to store in a database field. David Weininger, working at the U.S. EPA's Duluth laboratory, designed a line notation that writes a molecule as a short ASCII string — water is simply 'O', benzene is 'c1ccccc1'.

The Daylight theory manual stresses two properties that made the notation useful beyond being clever shorthand. SMILES is compact — a typical string takes 50–70% less space than an equivalent connection table — and canonicalization algorithms generate one unique SMILES per structure, so the name of a molecule can be synonymous with its structure and databases can use the string as a key.

Daylight Chemical Information Systems embodied the language in its toolkit, and most molecule editors and chemical databases came to accept SMILES as input. In 2007 the open-source chemistry community harmonized the dialects into OpenSMILES, confirming the notation as the field's common language.

One ASCII string names a whole molecule

A molecule fits in one short string, far smaller than a connection table

Canonical SMILES gives every structure one unique string for indexing

Most molecule editors and databases import it, making it the interchange default

It is human-readable enough for chemists to write by hand

Compactness plus canonicalization wins in data exchange: when every database stores the same string for the same molecule, the notation becomes the shared key of an entire industry.

OpenSMILES (2007) standardized the dialects, and today SMILES is the de facto exchange string across chemistry databases and toolkits; IUPAC's InChI covers canonical registry needs, while SMILES remains the human-friendly default.