There are three or four different Trend Micro extensions. According to this article from October, three of them only run on 32-bit Firefox: https://esupport.trendmicro.com/en-us/home/pages/technical-support/premium-security/1104395.aspx However, I think the bigger issue may be that no Legacy extensions can run in Firefox 57. You can check the list on the Add-ons page as follows. Either: * Ctrl+Shift+a (Mac: Command+Shift+a) * "3-bar" menu button (or Tools menu) > Add-ons * type or paste '''about:addons''' in the address bar and press Enter/Return In the left column of the Add-ons page, click Extensions. Then look above the list for a link to "Show legacy extension" and see whether Trend Micro's is there. Trend Micro has a toolbar (or at least a toolbar button) for Google Chrome, so they could probably convert that over to use in Firefox. The last response I saw on their forums was that there isn't a known time frame for that: https://en.community.trendmicro.com/tm_en/topics/the-new-firefox-v-57-0-quantum-does-not-accept-trendmicro-extension-anymore

thanks for your help.