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.