Polypane is a Chromium-based browser for front-end developers, designers, and quality-assurance teams. It displays a website in multiple synchronized viewports so users can develop and inspect responsive layouts, accessibility, performance, and page metadata without repeatedly resizing a conventional browser window.

Key Capabilities

Responsive development: Users can create panes from CSS breakpoints, device presets, or custom dimensions and view them simultaneously. Navigation, scrolling, clicks, hover states, keyboard input, form changes, and focus can be synchronized across panes.
Device and preference emulation: Each pane can emulate mobile or desktop rendering, touch input, orientation, device-pixel ratio, user agent, locale, text direction, safe-area insets, network conditions, and preferences such as dark mode, reduced motion, increased contrast, and forced colors.
Developer tools: Native tools inspect and edit elements across panes, consolidate console output and network requests, and expose cookies and browser storage. Chromium DevTools and selected DevTools extensions are also supported.
Accessibility testing: Polypane runs WCAG 2.2 audits and provides contrast checks, focus-order visualization, an accessibility tree, landmark and heading outlines, color-vision simulations, keyboard testing, and overlays for target size, text spacing, overflow, and other accessibility concerns.
Performance and metadata checks: Per-pane reporting covers Core Web Vitals and related measurements, including CLS, INP, LCP, FCP, and TTFB. Additional tools inspect canonical URLs, metadata, Open Graph tags, social-card previews, and structured page information.
Cross-browser review: Polypane Portal can open local or remote pages in external browsers and physical devices while synchronizing interactions for cross-browser testing and stakeholder review.
Development workflow support: Live reload watches project files and can inject changed CSS or images without a full-page refresh. Separate pane sessions allow teams to compare anonymous, authenticated, and administrative experiences side by side.

Audience & Use Cases

Polypane is intended for front-end developers, web designers, accessibility specialists, and QA teams. Typical uses include responsive-layout development, WCAG reviews, device and user-preference testing, browser debugging, performance checks, social-card validation, and sharing local work before it is deployed to a staging environment.

Technical Specifications

Application type: Desktop browser built with Electron and Chromium
Operating systems: Windows, macOS, and Linux
Rendering engine: Chromium
External-browser support: Polypane Portal for synchronized testing in other browsers and devices
Project configuration: Exportable projects and viewport workspaces stored as JSON
Browser extensions: Chromium DevTools extensions and limited support for regular Chromium extensions

Polypane’s built-in panes emulate device and browser properties within Chromium; they do not reproduce the rendering engines used by Safari or Firefox. Rendering defects specific to those engines must be verified in the corresponding browser, either independently or through Polypane Portal.

Polypane

What is Polypane?

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