Join MDN and developers like you at Mozilla's View Source conference, 12-14 September in Berlin, Germany. Learn more at

Parts of this page show the use of the XPInstall API. The majority of this API is now deprecated and as of Gecko 1.9 no longer available. Extension, Theme, and plug-in developers must switch away from install.js based packages to the new packaging scheme with an install.rdf manifest. In particular plugin developers should see how to package a plugin as an extension.


Full local path of the archive after it is downloaded to the platform specific temp folder. (e.g. C:\TEMP\argstest.xpi)
args can be passed in through the triggering APIs by attaching a ? and then the rg string to the xpi URL: (e.g. startSoftwareUpdate("http://webserver/argstest.xpi?ARGUMENT_STRING") will result in the value of Install.arguments being ARGUMENT_STRING #). Note that spaces in the arg string are legal. Everything after the question mark is treated as one string which becomes the Install.arguments property.
The application build ID in the form 20041231. Note that due to branching (different versions of Gecko with different feature sets might be built on the same day), using this property to "detect" the application version may produce false results. Additionally, the build ID can be 0 for custom builds.
Alias for archive
Contains information about the platform XPInstall was compiled for/runs on. For example, the value could begin with "Windows", "Macintosh" or "X11" (for Unix/Linux). For more details, see the corresponding code living in the GetInstallPlatform method of class nsInstall.
The fully qualified URL of the xpi (file URL, http URL, ftp URL, etc.) (e.g. http://dolfin/sgehani/zzz/ip.xpi). Note, even if triggered using relative URLs this will show the full URL (after qualification).

Document Tags and Contributors

 Contributors to this page: Sheppy, ethertank, trevorh, Daniel Veditz, Fredchat, Jens.B, Rod Whiteley
 Last updated by: Sheppy,