knobs

knobs is a free, open source alternative to Polypane and Sizzy for the checks most of us run every day: dark mode, locale, time zone, text size and device width. It runs inside the page you already have open, as a Chrome extension (also works in Edge) or as an npm package that you add to your own app in development only.

The same settings you find in the Rendering and Sensors tabs of Chrome DevTools sit in one panel on the page, and stay set while you work: color scheme, reduced motion, contrast, reduced transparency, text size and spacing, color blindness filters, locale and right-to-left text, time zone and the page clock, geolocation, user agent, offline, and the viewport with device frames for iPhone, Pixel, iPad and laptop. The extension can have Chrome set some of these for real through the debugger.

Grab copies an element with its html, the components that rendered it and their source files, ready to paste to a coding agent. MIT license.