I have developed an Firefox add on using the Add-on SDK. It is meant for my own personal use and is of no use to general Firefox users. It is also designed to be used on Desktop and Mobile (Android) versions of Firefox. I cannot recall exactly how I installed the add-on on my Android device but it has recently been disabled due to the recent security requirement that add-ons must be signed. Since then I have not been able to enable or reinstall the add-on from the XPI file. I am able to use the add-on on my Firefox for Windows. I did this by uploading the add-on to add-ons.mozilla.org, which, if I understand correctly, signs the add-on. So I have an unlisted signed add-on. To install this to my Firefox on Windows I do the following: 1. Visit https://add-ons.mozilla.org 2. Sign into my Firefox account 3. Navigate to Tools > Managed My Submissions 4. Click my unlisted add-on 5. Next to the 'Upload New Version' link I click the 'View All' link. 6. Click the current version of the add-on 7. Click the link for the add-on XPI file - this will install the add-on. I've tried this process on Firefox for Android but I'm not able to complete the process due to error when trying to log in. I've tried other things such as saving the XPI files to Google Drive, downloading it on the device and trying to load the file via the File System explorer but this doesn't work. I've tried upload the the XPI file to my own web site, creating a page with a link to the XPI and clicking the link. It appears Firefox is 'recognizing' that I'm trying to install an add-on but I get the message "Firefox prevent this site from asking you to install software on your device". Clicking 'Allow' doesn't appear to install the add-on. So it appears that the only way to install add-ons on Firefox for Android is via Tools > Add-ons from the menu. So how I am meant to install an unlisted add-on on Firefox Android?