Mozilla Firefox Quantum V66.0.5 Apr 2026

Automatically prevents websites from playing sound-enabled media.

Mozilla Firefox Quantum v66.0.5, released on May 7, 2019, was a critical point update primarily focused on resolving a significant bug that caused browser extensions to be disabled. Mozilla Firefox Quantum v66.0.5

The primary fix in v66.0.5 addressed a remaining issue where web extensions were still disabled for users with a master password set. released on May 7

Allows users to authenticate on websites using facial recognition or fingerprints on Windows 10. System Requirements Firefox 66.0.5 System Requirements Mozilla Firefox Quantum v66.0.5

A new ability to search through all open tabs via the tab overflow menu.

As part of the broader Firefox 66 release, this version includes:

Prevents web pages from "jumping" while images and advertisements load.