Polypane

A development browser that provides a multi-viewport environment for building responsive, accessible, and SEO-friendly websites. It solves the problem of manual resizing and testing across multiple devices by showing all breakpoints simultaneously with synchronized interactions. It is designed for professional web developers, designers, QA, and marketers who need to test and debug sites efficiently. It is positioned as a comprehensive alternative to standard browsers, offering built-in tools for accessibility, site quality, and emulation.

Key features

• Multi-viewport display
• Synced interactions across panes
• Device emulation
• Accessibility checking
• Link previews
• Image overlay
• Media query emulation
• Layout debugging
• Screenshot tools
• Color picker
• Elements panel
• Meta panel
• Outline panel
• Portal for cross-device testing