Polypane is a stand-alone browser with built-in tools for responsive design, accessibility, performance, meta info. Test you sites locally across different devices, user preferences, network conditions and check the quality of your pages across a wide range of simulators, debug tools and overviews. Polypane has everything you need in one developer tool: Powerful chromium-based devtools, multiple synced viewports, device emulation, media query emulation, over 25 different debug tools and over 80 different accessibility tests. View parts of your web page that you never see in clear overviews, like your meta info, document outline and more.