I am successfully installing custom installation of Firefox ESR, having modified some css code involving the sidebar. The part I'm struggling with is how to have installer recognize that I have included an extension that needs to be installed per profile. I have created a folder named "distribution", with a subfolder named "extensions" and have included the xpi file of my installation with the id surrounded by curly brackets as the fileName (so if filename is my id, my file is named: {filename}.xpi). This distribution folder is located in the same directory level as firefox.exe. Have I followed the steps provided here correctly? [[Deploying Firefox with extensions|https://support.mozilla.org/en-US/kb/deploying-firefox-with-extensions]] If so, I really don't know where to go from here. My xpi file works when loading from about:debugging and also works as a standard installation when using the xpi file directly.