.XPI File Format – install.rdf

Firefox add-on package

Before WebExtensions, a Firefox add-on described itself in install.rdf, at the top of the archive. Firefox stopped loading these add-ons in version 57, but old packages are still found. They often have a chrome.manifest beside it.

Structure

The file is an RDF document. Its details are in a Description element whose about attribute is urn:mozilla:install-manifest, with the properties in the namespace http://www.mozilla.org/2004/em-rdf#. Each property can be written as a child element, or as an attribute of the Description.

<RDF xmlns="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
     xmlns:em="http://www.mozilla.org/2004/em-rdf#">
  <Description about="urn:mozilla:install-manifest">
    <em:id>sample@example.org</em:id>
    <em:name>Sample Add-on</em:name>
    <em:version>1.0</em:version>
    <em:targetApplication>
      <Description>
        <em:id>{ec8030f7-c20a-464f-9b0e-13a3a9e97384}</em:id>
        <em:minVersion>3.0</em:minVersion>
        <em:maxVersion>3.6.*</em:maxVersion>
      </Description>
    </em:targetApplication>
  </Description>
</RDF>
PropertyHolds
em:idThe add-on’s ID.
em:nameIts name.
em:versionIts version.
em:descriptionA short description.
em:creatorWho made it.
em:homepageURLIts home page.
em:updateURLWhere to look for updates.
em:optionsURL, em:aboutURLThe add-on’s options and about pages.
em:typeA number saying what kind of add-on it is.
em:targetApplicationOne for each application it works with: em:id, em:minVersion and em:maxVersion.

The application ID {ec8030f7-c20a-464f-9b0e-13a3a9e97384} is Firefox.

install.js

Older packages have no install.rdf. They hold an install.js script that ran under Mozilla’s XPInstall installer and carried out the installation itself.