4-Aminoindole is primarily used as a key intermediate in the synthesis of pharmaceuticals and biologically active compounds. Its structure makes it valuable in the development of kinase inhibitors, which are important in cancer therapy. It is also employed in the production of serotonin receptor modulators and other neuroactive agents. Due to the presence of both amine and indole functionalities, it serves as a versatile building block in medicinal chemistry for constructing complex heterocyclic systems. Additionally, it finds use in the research and development of dyes and fluorescent probes, especially in biochemical labeling and imaging applications.