Due to advances in technology and the availability of participant databases, online experiments have become very popular in recent years. However, in an online environment it is not possible to control hardware and software settings to the same extent as in a laboratory. However, control or accurate knowledge of these parameters is important for accurate timing. As a result, early research was sceptical about whether time-critical experiments, and in particular masked priming effects, could be achieved online. Several published studies now report the general feasibility of masked priming online, but none of these studies included a stringent measure of awareness. In addition, the precision of stimulus presentation is usually not reported, so it is not clear whether accurate stimulus presentation was achieved or not.
I will present a pre-registered masked number priming experiment addressing these points. Results showed that masked priming effects can indeed be obtained online, even under conditions of zero awareness. Descriptive analyses of the technical parameters showed that there was considerable variation in precision, but that the results hold still significant when only precise timing trials were considered. Given these results, researchers should not simply trust an effect obtained online, but should implement reports and criteria regarding important technical parameters and presentation precision.