To prevent the browser from automatically upgrading you to version 4.0+, you must visit the Greasemonkey entry in your Add-ons Manager and set "Automatic Updates" to Off . Safety and Modern Alternatives
While version 3.17 is useful for legacy setups, it does not receive security updates. For users on modern versions of Firefox or Chrome, it is generally recommended to use the latest version of Greasemonkey or alternatives like Tampermonkey or Violentmonkey for better performance and security. Greasemonkey stopped working in 52 esr - Mozilla Support
If you are using a compatible browser and need this specific version, you can find it through official archives: greasemonkey 3.17 download
Many veteran users prefer the original "Monkey Menu" and management interface of the 3.x branch compared to the redesigned menus in current versions. Key Features and Changes in 3.17
In your browser, go to about:addons , click the gear icon, and select "Install Add-on From File" to select the downloaded 3.17 .xpi . To prevent the browser from automatically upgrading you
Scroll down to the older versions. Even if a "Not compatible with your browser" warning appears, you can still download the .xpi file manually.
Greasemonkey 3.17 is a significant milestone in the history of Firefox extensions, serving as the final "legacy" version of the popular userscript manager. For many power users, it remains a vital tool for maintaining compatibility with classic browser environments and older scripts that do not function correctly in modern WebExtension-based versions. Greasemonkey stopped working in 52 esr - Mozilla
Some older userscripts rely on APIs (like GM_getResourceURL or certain GM_xmlhttpRequest behaviors) that were deprecated or changed in the transition to version 4.0.