Basilisk vs Polypane

Basilisk is an open-source web browser based on the Goanna rendering engine, a fork of Mozilla's Gecko. It aims to provide a classic browser interface with XUL extension support while maintaining modern web standards compatibility.

Polypane is Browser built for web developers, showing multiple viewports simultaneously with built-in accessibility and layout debugging tools.. It is available under a paid model. This tool falls under the browsers category.