We are planning to deprecate the use by Firefox add-ons of the techniques described in this document.

Don't use these techniques to develop new add-ons. Use WebExtensions instead.

If you maintain an add-on which uses the techniques described here, consider migrating it to use WebExtensions instead.

Add-ons developed using these techniques might not work with multiprocess Firefox (e10s), which is already the default in Firefox Nightly and Firefox Developer Edition, and will soon be the default in Beta and Release versions of Firefox. We have documentation on making your add-ons multiprocess-compatible, but it will be more future-proof for you to migrate to WebExtensions.

A wiki page containing resources, migration paths, office hours, and more, is available to help developers transition to the new technologies.


Information about the application on which your add-on is running.

With the exception of ids, each of these properties exposes the attribute of the same name on the nsIXULAppInfo interface. For more information, see the MDN documentation.




Checks whether the host application is the given application.


name : string
A host application name.


boolean : True if the host application is name and false otherwise.


Checks whether the host application is one of the given applications.


names : array
An array of host application names.


boolean : True if the host application is one of the names and false otherwise.

versionInRange(version, lowInclusive, highExclusive)

Compares a given version to a version range. See the MDN documentation for details on version comparisons.


version : string
The version to compare.

lowInclusive : string
The lower bound of the version range to compare. The range includes this bound.

highExclusive : string
The upper bound of the version range to compare. The range does not include this bound.


boolean : True if version falls in the given range and false otherwise.



The GUID of the host application. For example, for Firefox this value is "{ec8030f7-c20a-464f-9b0e-13a3a9e97384}".


The host application name. The possible values here are:

  • "Firefox"
  • "Fennec"
  • "Mozilla"
  • "SeaMonkey"
  • "Sunbird"
  • "Thunderbird"

"Firefox"and"Fennec"` are the most commonly used values.


The host application version.


The Gecko/XULRunner platform version.


A mapping of application names to their IDs. For example, ids["Firefox"] == "{ec8030f7-c20a-464f-9b0e-13a3a9e97384}".

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