If you want “old but not ancient,” try (from mid-2020). It still supports classic extensions with some backported fixes, runs on Windows 7, and works with 90% of the modern web. You can disable updates easily and freeze your environment.
Using an old version of Firefox comes with significant security trade-offs that every user must acknowledge: old version firefox
Modern Firefox versions have dropped support for older systems. For instance, users on Windows 7, 8, and 8.1, as well as macOS 10.12 through 10.14, often rely on Firefox 115 ESR to continue browsing securely. If you want “old but not ancient,” try (from mid-2020)
The primary reason users cling to old versions of Firefox—specifically versions prior to the "Quantum" update (version 57) in 2017—is the architecture of add-ons. For over a decade, Firefox was defined by its powerful extension system, XUL (XML User Interface Language). This system allowed developers to change almost every aspect of the browser. Extensions like "Classic Theme Restorer" or specific developer tools could dig deep into the browser’s skeleton. When Mozilla switched to the WebExtensions API to modernize the browser and improve stability, they effectively killed off thousands of legacy add-ons. For power users who relied on specific workflows that were only possible through these deprecated extensions, the "new" Firefox was functionally useless. Thus, they stayed behind, preferring a browser that worked their way over a browser that was modern. Using an old version of Firefox comes with
Let’s be honest: ❌ No modern TLS 1.3 on very old versions (pre-52) ❌ No H.264 or AV1 video support in many cases ❌ Many websites will complain or break (looking at you, Figma and new Reddit) ❌ Security vulnerabilities — so never use old Firefox with sensitive accounts or random Wi-Fi
