Polypane

Polypane is a Chromium-based browser for web developers and designers that shows a site in several panes at once. Each pane can emulate a real device, use the responsive CSS breakpoints of the site or custom dimensions, from mobile to 5K screens, so that layouts can be checked without resizing the browser.

Scrolling, clicks and keyboard input are synchronised across all panes. The same page can be displayed side by side with different user preferences, such as dark and light mode, high contrast or reduced motion. Built-in panels check structure, metadata and accessibility while the page is used, which helps find layout and accessibility issues during manual and exploratory testing of web pages.

Polypane runs on Windows, macOS and Linux. It is a commercial product sold by monthly or yearly subscription, with a 14-day free trial.