: This era was the last to support plugins like Java , Silverlight , and Adobe Acrobat . Modern browsers have disabled these for security, but certain industrial or legacy internal company portals still require them. Version Highlights: A Quick Reference Version Range Key Milestone Firefox 12–51
Downloading and using old versions of Firefox is on the modern web. These versions: Legacy Add-on Support on Firefox ESR - The Mozilla Blog Download Firefox 12-51 52 Esr
The long-term support version that became a "safe haven" for users needing legacy compatibility until late 2018. Important Security Warning : This era was the last to support
Re-enabled non-Flash plugins temporarily and improved text input for third-party keyboards. These versions: Legacy Add-on Support on Firefox ESR
: Versions in this range supported older Mac OS versions like 10.9 (Mavericks) through 10.12 (Sierra).
The "Rapid Release" era characterized by the steady introduction of HTML5 features and the classic extension ecosystem.
Understanding the Legacy: Firefox Versions 12–51 and 52 ESR