Polypane is a specialized browser built from the ground up for web development that displays multiple synchronized viewports side by side, enabling developers to test responsive designs, accessibility, and cross-device compatibility simultaneously. It solves the tedious workflow of repeatedly resizing browser windows or switching between device emulation modes by showing how a page looks across multiple screen sizes at once, with all viewports synchronized for scrolling, navigation, and interactions. Polypane is designed to replace the standard browser as the primary development tool for building responsive web applications.
Polypane features synchronized multi-viewport browsing with customizable device presets, built-in accessibility auditing including contrast checking, focus order visualization, and screen reader simulation, a comprehensive CSS debugging overlay system, live CSS editing with persistence, meta tag and social media preview inspection, dark mode simulation, and detailed performance metrics per viewport. It also provides handy development utilities like a color picker, screenshot tool with full-page capture across all viewports, reference image overlay for comparing designs, and element inspection that highlights the same element across all viewports simultaneously.
Polypane is designed for frontend developers, web designers, and accessibility specialists who spend significant time building and testing responsive, accessible web interfaces. It integrates with local development servers, supports browser extensions, and works with any web technology stack. Polypane is particularly valuable for developers working on design systems, responsive email templates, and applications that must meet WCAG accessibility standards, as its multi-viewport approach and built-in accessibility tools dramatically reduce the time spent on responsive and accessibility testing compared to using standard browser developer tools.
