How to open .XPI files on Linux
To open .XPI files on Linux, to install (when permitted): use Firefox’s Add-ons/Extensions manager and install the .xpi through Firefox’s UI.
Step-by-step instructions
- To install (when permitted): use Firefox’s Add-ons/Extensions manager and install the .xpi through Firefox’s UI.
- To inspect: open/extract it with a ZIP tool; Linux desktops may map .xpi via the shared MIME-info database rules for extensions.
Common issues
Firefox won’t install the XPI (blocked or incompatible)
Firefox may refuse an XPI if it is not compatible with your Firefox version or if installation from a file/source is restricted. Extension packaging and compatibility expectations changed significantly around Firefox 4 and later.
- Confirm the add-on is intended for your Firefox version and extension type (legacy vs. WebExtension packaging).
- Try installing through Firefox’s add-ons manager rather than treating it as a regular file.
- If it still fails, inspect the XPI as a ZIP to verify it contains the expected extension files/metadata.
The XPI downloads but doesn’t install from a website
Web servers may need to serve .xpi with the expected MIME type so browsers recognize it as an installable add-on package instead of a generic download.
- If you manage the website, configure the server to send the MIME type commonly used for XPI: application/x-xpinstall (as documented by Mozilla).
- If you are a user, save the file and use Firefox’s add-on installation flow; if that still fails, the add-on may be blocked or not compatible.
Archive tools say the file is corrupt or won’t open
An XPI is a ZIP archive; if download was interrupted or modified, ZIP tools may fail to read it.
- Re-download the .xpi from its original source to ensure it is complete.
- Try opening it with another ZIP-capable tool to confirm whether the archive is actually damaged.
- If it opens, extract to a folder rather than trying to view-in-place.
Signature-related problems (unsigned or signature missing)
Firefox add-ons use signing artifacts inside the XPI (for example under META-INF) and Firefox may enforce signing requirements depending on configuration/version.
- Inspect the XPI contents as a ZIP and check for signature-related files (such as entries under META-INF) if you are troubleshooting.
- If Firefox requires signed add-ons, obtain a properly signed build from a trusted source rather than trying to bypass checks.
Security note
Treat .xpi files as executable add-on packages, not just “documents”: installing an untrusted XPI can grant code running in the browser significant capabilities.