.XPI File Extension

.XPI File Extension

File Type

Cross-platform Installer Package

Developer Mozilla
Popularity
4.1  |  681 Votes
Category Plugin Files
Format Zip

What is an XPI file?

An XPI file is a compressed installation archive used by various Mozilla applications, including Firefox, Thunderbird, and SeaMonkey. It contains an app add-on, such as a Firefox plug-in, toolkit, or theme. Most XPI files include an install.js, install.rdf, or readme.md file, which contains the add-on's installation instructions.

More Information
Screenshot of a .xpi file in Apple Finder
XPI file open in Apple Finder

XPI files are essentially renamed .ZIP archives that Mozilla applications use to install add-ons. These archives often contain .JS, .CSS, .HTML, and .JSON files that, combined, comprise the code needed to install an add-on. Add-ons that use icons and other images also contain .PNG files.

How do I open an XPI file?

Some versions of Mozilla Firefox allow you to install an XPI file by dragging and dropping it onto an open browser window. Firefox then uses a component called XPInstall to install the add-on the XPI file contains.

If dropping your XPI file onto Firefox does not work, you can manually install the file using the instructions below:

  1. In Windows, select the Menu (three horizontal line) icon in Firefox's upper-right corner and click Add-ons. (In macOS, select Tools → Add-ons.)
  2. Select Extensions, Themes, or Plugins (depending on the type of add-on your XPI file contains).
  3. Click the Gear icon dropdown menu and select Install Add-on From File....
  4. Navigate to and select your XPI file. Then, click Open.

How do I install an XPI file in Mozilla Thunderbird?

To install an XPI file in Mozilla Thunderbird:

  1. In Windows, select the Menu (three horizontal lines) icon, click Add-ons, and then click Add-ons again. (In macOS, select Tools → Add-ons.)
  2. Select Extensions, Themes, or Plugins (depending on the type of add-on your XPI file contains).
  3. Click the Gear icon dropdown menu and select Install Add-on From File....
  4. Navigate to and select your XPI file. Then, click Open.

How do I view an XPI file's contents outside Mozilla applications?

Since an XPI file is a Zip-compressed archive, you can manually extract and view its contents by:

  1. Renaming the file to use the .zip extension.
  2. Extracting the file's contents with a Zip compression utility, such as Corel WinZip (Windows, Mac), 7-Zip (Windows), or Apple Archive Utility (Mac).
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Programs that open XPI files

Updated July 12, 2021

Verified by FileInfo.com

The FileInfo.com team has independently researched the Cross-platform Installer Package file format and Mac, Windows, and Linux apps listed on this page. Our goal is 100% accuracy and we only publish information about file types that we have verified.

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