Window Resizer is a Chrome extension that resizes your actual browser viewport to preset or custom device dimensions on any site you're visiting.
Unlike devtools' responsive mode, which simulates a viewport inside the existing browser chrome, this resizes the real window: so you see how a live site behaves at an exact width, including scrollbars and OS-level rendering quirks that emulation can mask.
Use it for a fast breakpoint sanity check on your own just-shipped site, or to see how a competitor's layout actually collapses at a specific width, without opening devtools each time.
It needs permission to run on all sites, which is standard for what it does, but worth knowing if you're auditing extension permissions before installing it on a work machine.
A browser extension for resizing your viewport to test responsive layouts.
