Most responsive edge cases don’t appear during testing. They show up during real usage, at slightly “wrong” viewport widths.

This Chrome extension randomly shifts the viewport width to realistic values while you use your site normally.

The goal is passive exposure, not active testing: you keep working, and edge cases surface on their own.

Repo (Chrome Web Store approval pending, local install for now):

https://github.com/pavel-voronin/chrome-random-viewport

Feedback welcome.