Indolyl is a molecule that contains the indole functional group. It is commonly found in various natural compounds such as the amino acid tryptophan, which is a precursor of serotonin and melatonin. Indolyl compounds have been found to possess a wide range of biological activities such as anti-inflammatory, antibiotic, anticancer, and neuroprotective properties. Synonyms for indolyl include indole, indol-3-yl, 1H-indol-3-yl, and benz[b]indol-3-yl. These synonyms are frequently used in research articles, drug discovery, and pharmaceutical industries. Indolyl compounds have also been used as chemical probes to study various biological processes and as building blocks for the synthesis of novel drug candidates.