Basilisk is a XUL-based web-browser demonstrating the Unified XUL Platform (UXP). This browser is a close twin to pre-Servo Firefox in how it operates. It is based on the Goanna layout and rendering engine (a fork of Gecko) and builds on the Unified XUL Platform (UXP), which in turn is a fork of the Mozilla code base without Servo or Rust. Basilisk is primarily a reference application for development of the XUL platform it builds upon, and additionally a potential replacement for Firefox.

It supports a wide array of features required for the Modern Web, including advanced scripting, CSS, HTML5 and downloadable font support. It also fully supports all NPAPI plugins (e.g. Java, Unity web player, Media plugins, Authentication plugins).