GBL is a chemical used mainly in cleaning and industrial products but it is also a “precursor” to GHB, a drug that can make you feel very relaxed and happy. This means that when you take GBL, it changes into GHB in your body. This is one way that people get around the strict laws governing GHB because while GBL is also illegal as a recreational drug, it is still widely available in many easy-to-obtain products.