The Geprüfte Sicherheit ("Tested Safety") or GS mark is a voluntary certification mark for technical equipment. It indicates that the equipment meets German and, if available, European safety requirements for such devices. The main difference between GS and CE mark is that the compliance with the European safety requirements has been tested and certified by a state-approved independent body. . A CE Mark, in contrast, is issued for the signing of a declaration that the product is in compliance with the standards. The mark is based on the German Equipment and Product Safety Act ("Geräte- und Produktsicherheitsgesetz", or "GPSG").

Although the GS mark was designed with the German market in mind, it appears on a large proportion of electronic products and machinery sold elsewhere in the world.

Any electrical, mechanical or electro-mechanical product bearing the GS Mark indicates that it was tested and complies with the minimum requirements of the German Equipment and Product Safety Act (a.k.a. GPSG). The GS Mark (Geprüfte Sicherheit, meaning Safety Tested) is a licensed mark of the German government and may only be issued by an accredited product safety testing and certification agency.

Strong reasons for bearing the GS Mark
The GS Mark, although strictly voluntary, is highly regarded by German consumers and manufacturers alike. In fact products not bearing the mark, whether consumer or commercial, are nearly impossible to sell in Germany. The GS Mark also lends itself as a powerful marketing tool throughout Europe because it symbolizes safety and quality and instills a strong sense of confidence among consumers.