Gamma-butyrolactone (GBL) is an industrial chemical commonly used as a solvent and chemical intermediate in various products such as paint removers, cleaners, adhesives, and nail polish removers. It is also known as a precursor to gamma-hydroxybutyric acid (GHB), a schedule I depressant that gained notoriety as a date rape drug and is illicitly used as a substitute and chemical precursor to GHB. GBL is converted into GHB in the body, and its effects are identical to GHB, but it is two to three times as powerful and its effects are felt faster, making it a greater risk for overdose. GBL is classified as a Schedule I controlled substance in the US, and its use is associated with serious safety concerns, including the risk of overdose and adverse reactions when used in combination with other substances.

In summary, GBL is an industrial chemical with various commercial uses, but it is also associated with illicit use as a substitute for GHB, with potential serious health risks and legal implications.