Either your own or RealEye participants. You can invite your users or panel and share the study with them using a participation link. All they need to have is a laptop/PC with a webcam.
We also have a network of panelists from all over the world - mainly from the UK and the US. Randomly picked users can be assigned to your task. They are called RealEye participants. We will not show them your stimuli before the test starts, so their interaction will be natural.
Note: RealEye participants can't take part in a 'Live Website' studies and studies longer than 10 minutes. Read more about the limitations here