Abstract: Examples of emulating a web browser for a system under test are disclosed. In one example implementation according to aspects of the present disclosure, a controller module emulates a plurality of virtual web browsers for a plurality of simulated users. A plurality of injector modules hosts the virtual web browsers with at least one of the plurality of injector modules being self-designating as a master injector module and the remaining plurality of injector modules being designated as slave modules. A system under test module provides web content to the virtual browsers being emulated on the plurality of injector modules.