Review paperResistance spot welding (RSW) is a metal joining method that is widely used, especially in the automotive industry. Welding technologies are also developing in parallel with the developments in the industry. Traditional alternating current resistance spot welding systems (AC-RSW) are being replaced by new generation medium frequency direct current resistance spot welding (MFDC-RSW) systems. In addition, MFDC-RSW is one of the high energy efficient methods that can work in harmony with robots that have an important role in Industry 4.0. In this study, resistance welding methods, which have an important place in welding technology, are classified and the developments in the new generation MFDC-RSW systems are examined. The advantages and disadvantages of the stated welding method are compared with conventional AC-RSW systems. In addition, the inverter topology of MFDC-RSW systems based on power electronics technology has been examined.