Virtual Chinrest Task
The participant fixates a black square. A red circle moves laterally, and the participant indicates when the red circle disappears (indicating it passes the blind spot) by pressing the space bar. Based on Li et al (2020). See also this page about calibration of dimensions for other options.
Note that this does not currently deal with window resizing during the task. Please let us know if you need this functionality.
Li, Q., Joo, S. J., Yeatman, J. D., & Reinecke, K. (2020). Controlling for Participants’ Viewing Distance in Large-Scale, Psychophysical Online Experiments Using a Virtual Chinrest. Scientific Reports, 10(1), 904.