How to Install an XPI File
If you're using the Mozilla Firefox Browser there's a good chance that at one time or another you've installed an XPI file and didn't even know it. XPI files are compressed installation archives that are meant for Firefox programs. They are easy to install directly onto your Firefox browser, whether you're an expert Windows users or a beginner to the world of PCs.
Find the program/add-on you want to install on your Firefox browser and download the file to your Windows mobile desktop. It doesn't matter what version of Windows that you're using, as the program is meant for your Firefox installation, not for your desktop OS.
Make sure you have a new Firefox window open. If you don't have the browser open, launch it from your desktop or any other location on your PC.
Drag the XPI file you have downloaded on your computer to your browser window by holding down your left mouse button over the XPI file and using your mouse to drag the file directly into the middle of your browser screen and then letting go of your left mouse button.
Click the "Yes" option when asked if it's okay to install the file on the browser.
Wait for the XPI file to complete the install process. Firefox will then tell you that it's necessary to perform a browser restart for the changes to take place; click the "Restart" button when it appears. Wait for your browser to close and reopen after pushing "Restart." Your XPI file is now installed.
Verify that the file is installed by clicking on "Tools" via the top of your Firefox broswer. You should then see the application on the list.
Tips & Warnings
- Always verify the legitimacy of XPI programs before downloading and using the apps to ensure you are not receiving malicious software.