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Basilisk 2020.04.17 [Update]


Basilisk is a free and Open Source XUL-based web browser created by the developers of the Pale Moon browser. 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 as an application is primarily a vessel for development of the XUL platform it builds upon, and additionally a potential replacement for Firefox to retain the use of Firefox Extensions. It aims to retain useful technologies that its sibling Firefox has removed.

Requires Windows 7 or later. Windows XP or Windows Vista are not supported.

Main features:

  • Full support for JavaScript's ECMAscript 6 standard for modern web browsing.
  • Support for all NPAPI plugins (Unity, Silverlight, Flash, Java, authentication plugins, etc.).
  • Support for XUL/Overlay Mozilla-style extensions.
  • Experimental support for WebExtensions (in gecko-target mode). Please note that some Mozilla-specific WebExtension APIs are not yet available.
  • Support for ALSA on Linux.
  • Support for WebAssembly (WASM).
  • Support for advanced Graphite font shaping features.
  • Support for modern web cryptography: up to TLS 1.3, modern ciphers, HSTS, etc.

Important differences with Mozilla Firefox:

  • Uses Goanna as a layout and rendering engine. Goanna behaves slightly differently than Gecko in certain respects and may result in different display of web pages. e.g.: Goanna renders gradients in a more accurate color space (non-premultiplied).
  • Builds on UXP, our XUL platform in development. As such XUL is alive and well in this browser and will not be deprecated.
  • Has some long-standing known issues with the Mozilla code-base fixed (e.g. CVE-2009-1232).
  • Does not use Rust or the Photon user interface. You can expect a familiar interface as-carried by Firefox between v29 and v56.
  • Does not use Electrolysis (e10s, multi-process browsing).
  • Does not require walled-garden extension signing.

Basilisk 2020.04.15 release notes:

This is a major development update. Important: It is possible that since 2020.03.04 your browser is no longer checking automatically for updates, due to an oversight in keeping a pre-release preference. You may have to check for updates manually from the About box. Please verify after updating that your updating preferences are set correctly for your use!

Basilisk 2020.04.15 changelog:

  • Changed site-specific overrides to use an operating system macro instead of hard-coding a version.
  • Changed the way hardware acceleration is set on various operating systems.
  • Fixed an incorrect preference preventing automatic updates by default.
  • Changed the geolocation service requests to https thanks to a generous service donation by
  • Changed the security storage database type to SQLite.
  • Enabled AV1 support in all builds; this was erroneously not built in recent releases.
  • Fixed several potential crashes.
  • Re-imported the ExtensionStorage js module for use by browser extensions.
  • Removed the use of high-resolution Windows system timers from the layout refresh driver; this should help with some performance and battery life issues.
  • Fixed an issue with element outlines sometimes being drawn too large.
  • Fixed an issue with grid cell sizing.
  • Fixed an issue with layout frames (e.g. selection popups) being wrongly positioned.
  • Removed a potentially dangerous and otherwise ineffective optimization from the JavaScript engine.
  • Fixed unwanted behavior where created/focused pop-up windows could potentially cover the DOM fullscreen notification, hiding it from users. (CVE-2020-6810)
  • Fixed an issue where copying data as a curl request from developer tools would not properly escape parameters. (CVE-2020-6811)
  • Updated our sctp library code with several upstream fixes.
  • Fixed an issue with the release of document content viewers (CVE-2020-6819). Defense-in-depth.
  • Fixed an issue with handling functions with rest parameters. Defense-in-depth.
  • Removed HTTP Public Key Pinning (HPKP)
  • Removed HSTS preloading list support since these lists are no longer efficient.

Changes in Basilisk 2020.04.17:

  • Enabled building of AV1 codec support (for real this time).

Download: Basilisk 2020.04.17 (32-bit) | Portable | ~50.0 MB (Open Source)
Download: Basilisk 2020.04.17 (64-bit) | Portable
View: Basilisk Website

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