I feel bad for the author that this extension has such a low rating, which seems to stem mostly from people who review-bombed it years ago over limitations Mozilla implemented.
I will say that the overall UX is not super intuitive, but as a web developer working with multiple windows at various viewport sizes, having adjacent windows readjust themselves is such a timesaver.
Until FancyZones implements this feature (https://github.com/microsoft/PowerToys/issues/254), this is a great free browser alternative to tools like AquaSnap.
