This chapter focuses on de facto standards, which are usually developed by private parties rather than standard setting organizations (SSOs). In the ICT sector there are numerous examples of de facto standards, including IBM PC architecture, computer instruction set architecture, operating systems, formats and human-machine interfaces. De facto standards also lead to competition issues just as de jure standards do, such as abuse of dominance and the holdup problem, whether by other IP holders or the setters of de facto standards.