Screen resolution differ between online and offline experiment

Hi! I’m creating an online experiment. I have added a custom javascript code in order to get windows information;

window_width = psychoJS.window.size[0]
window_height = psychoJS.window.size[1]

My screen is 1920x1080 and when I run the script offline I have the same info. Unfortunately when I run the experiment online the resolution is lower (1920x947). Is it normal? I did not change monitor settings.

This is the experiment link

Is it running full screen, or can you still see the browser toolbars and so on?