A method and system for estimating a screen refresh rate of a computing unit participating in an Internet-based collaboration. The computing unit receives a test image that includes pixels located at predefined positions and blinking at predefined frequencies. Measurements of the number of blinks of the pixels in a specified time period are collected. An average of the measurements summed over the predefined frequencies is calculated. A screen refresh rate is estimated by comparing the calculated average to a sum of multiple sums of simulated blinks of pixels in the specified time period. The average is closer to the sum than any of the other sums and the sum is associated with the estimated screen refresh rate.