By combining the effects of contact electrification and electrostatic induction, triboelectric nanogenerators (TENGs) can effectively convert mechanical energy into electric power or signals. Over the past decade, TENG development has progressed rapidly, from fundamental scientific understanding to advanced technologies and applications. This Primer gives a brief overview of TENGs, including the mechanisms of contact electrification and electrodynamics, applications, future opportunities and limitations. As an interdisciplinary field, advances are expected in both theoretical and experimental aspects of TENGs. For example, technologies based on Maxwell’s equations for a mechano-driven, slow-moving system can be coupled with a theoretical understanding of physical laws and concepts. From this, general simulation models can be established and corresponding experiments designed to optimize TENGs for a range of applications.