My screen resolution isn't shown accurately on this tool. It returns 1920x1080x32, but my actual window resolution is something like 1880x1020x32 (I use swaywm

My screen resolution isn't shown accurately on this tool. It returns 1920x1080x32, but my actual window resolution is something like 1880x1020x32 (I use swaywm and leave gaps around windows for a border). If I resize the window to 300x700, the tool returns 1440x900x32. If I disable all my extensions and Firefox's enhanced tracking protection, it always returns 1920x1080x32. I'm using swaywm, so maybe this is an (unintentional?) feature of wayland.