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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.


Compares the version of a file or package with the version of an existing file or package.

Method of

InstallTrigger object


int compareVersion (
   String registryName,
   InstallVersion version);

int compareVersion (
   String registryName,
   String version);

int compareVersion (
   String registryName,
   int major,
   int minor,
   int release,
   int build);


The compareVersion method has the following parameters:

The pathname in the Client Version Registry for the component whose version is to be compared. This parameter can be an absolute pathname, such as /royalairways/RoyalSW or a relative pathname, such as plugsin/royalairway/RoyalSW. Note that the registry pathname is not the location of the software on the computer; it is the location of information about the software inside the Client Version Registry.
An InstallVersion object containing version information or a String in the format, where major, minor, release, and build are integer values representing version information.


If the versions are the same or if Software Installation is not enabled, this method returns 0. If the version of registryName is smaller (earlier) than version, this method returns a negative number. Otherwise, this method returns a positive number. In particular, this method returns one of the following values:

component not present or not registered.
registryName has a smaller (earlier) major number than version.
registryName has a smaller (earlier) minor number than version.
registryName has a smaller (earlier) release number than version.
registryName has a smaller (earlier) build number than version.
The version numbers are the same; both objects represent the same version.
registryName has a larger (newer) build number than version.
registryName has a larger (newer) release number than version.
registryName has a larger (newer) minor number than version.
registryName has a larger (newer) major number than version.

The following constants can be used to check the value returned by compareVersion:

int MAJOR_DIFF = 4;
int MINOR_DIFF = 3;
int REL_DIFF = 2;
int BLD_DIFF = 1;
int EQUAL = 0;

In Communicator 4.5, the following constants are defined and available for checking the value returned by compareVersion:



The compareVersion method compares the version of an installed file or package with a specified version. It is often used as a check against which to initiate the installation process. If registryName is not found in the Client Version Registry or if registryName does not have version, registryName is assumed to have a version of If registryName represents a file, compareVersion checks for the existence of the file. If the file has been deleted, its version is assumed to be

Document Tags and Contributors

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