From MozillaZine Knowledge Base

Most of information here applies to install.rdf used in themes too. See below for detailed information.

Firefox 0.9, Thunderbird 0.7, Nvu 0.? and all subsequent versions of these products use the Extension Manager ("the EM") for managing extensions and themes. In order to have your extension supported by it you have to package your extensions as described in "Packaging Firefox/Thunderbird Extensions" document at mozilla.org (see also documentation at Devmo). This includes providing a valid install.rdf file.

Creating install.rdf using tools

You can use any of these tools:

• Extension developer's extension has Extension Builder functionality.
• Ted Mielczarek's webapp for install.rdf creation.
• Ted Mielczarek's Extension Wizard for Firefox/Thunderbird version 1.5 and above (discussion thread at MZ forums).
• xpiZilla - Windows-only install.rdf and XPI generator by Will Ryan (disscussion thread at MZ forums).
• Extensionmaker - A Tcl Starkit for Windows that generates an install.rdf. You need a tclkit runtime for Windows to start it (see [1]). It's currently beta.

Template

If you choose to manually create an "install.rdf" file, you can use the template below as a guide.

<?xml version="1.0"?>
<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>{XXXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX}</em:id>
		<em:name>Sample Extension</em:name>
		<em:version>1.0</em:version>
		<em:description>A sample extension with advanced features</em:description>
		<em:creator>Your Name Here</em:creator>
		<!-- optional items -->
		<em:contributor>A person who helped you</em:contributor>
		<em:contributor>Another one</em:contributor>
		<em:homepageURL>http://sampleextension.mozdev.org/</em:homepageURL>
		<em:optionsURL>chrome://sampleext/content/settings.xul</em:optionsURL>
		<em:aboutURL>chrome://sampleext/content/about.xul</em:aboutURL>
		<em:iconURL>chrome://sampleext/skin/mainicon.png</em:iconURL>
		<em:updateURL>http://sampleextension.mozdev.org/update.rdf</em:updateURL>
		<em:type>2</em:type> <!-- type=extension --> 

                <!-- Firefox -->
		<em:targetApplication>
			<Description>
				<em:id>{ec8030f7-c20a-464f-9b0e-13a3a9e97384}</em:id>
				<em:minVersion>0.9</em:minVersion>
				<em:maxVersion>1.0</em:maxVersion>
			</Description>
		</em:targetApplication>

                <!-- This is not needed for Firefox 1.1 and later. Only include this 
                     if you want to make your extension compatible with older versions -->
		<em:file>
			<Description about="urn:mozilla:extension:file:sampleext.jar">
				<em:package>content/</em:package>
				<!-- optional items -->
				<em:skin>skin/classic/</em:skin>
				<em:locale>locale/en-US/</em:locale>
				<em:locale>locale/ru-RU/</em:locale>
			</Description>
		</em:file>
	</Description>

</RDF>

Target applications' GUIDs

Notes

• Mozilla Suite ignores install.rdf, but you ought to include corresponding targetApplication item in install.rdf if you support the Suite and are going to submit your extension to update.mozilla.org, see this thread. You still must include an install.js file if you support Mozilla Suite.
• "SeaMonkey" is now the name of the community project, that continues working on the Mozilla Suite codebase, after Mozilla Foundation has announced it will not actively develop the Mozilla Suite any further. At the moment it doesn't read install.rdf, just as the Mozilla Suite, but it's planned to implement this in future.
• The em:type arc was introduced in Toolkit 1.1a applications. It's used to specify the type of an item. Use the value of 2 for extensions, 4 for themes.

Items' IDs

Each extension must have a unique ID (the value of em:id arc).

Initially, it was recommended to use GUIDs for extensions IDs. To generate a GUID, you can use MS guidgen (a GUID generator for Windows NT-based systems), uuidgen (for *nix, also comes with MSVS), a web-based generator such as this and this, or open your IRC client, go to irc://irc.mozilla.org/botbot and say 'botbot uuid'.

Extension Manager in Toolkit 1.5-based applications will not install extensions using arbitrary strings as their IDs. Only GUIDs and IDs of extension@domain form are now accepted. For example, the DOM Inspector has inspector@mozilla.org ID.

Versioning

See Toolkit version format document for details about version's format used.

install.rdf for themes

TBD. See [2]. The main difference is the additional "em:internalName" arc in theme's manifest.