AIR applications first require the runtime to be installed on a user's computer, just as SWF files first require the Flash Player browser plug-in to be installed.

The runtime is installed to the following location on a user's computer:

• Mac OS: /Library/Frameworks/

• Windows: C:\Program Files\Common Files\Adobe AIR

• Linux: /opt/Adobe AIR/

On Mac OS, to install an updated version of an application, the user must have adequate system privileges to install to the application directory. On Windows and Linux, a user must have administrative privileges.

The runtime can be installed in two ways: using the seamless install feature (installing directly from a web browser) or via a manual install. For more information, see Distributing, Installing, and Running AIR applications.

The seamless install feature provides developers with a streamlined installation experience for users who do not have Adobe AIR installed yet. In the seamless install method, the developer creates a SWF file that presents the application for installation. When a user clicks in the SWF file to install the application, the SWF file attempts to detect the runtime. If the runtime cannot be detected it is installed, and the runtime is activated immediately with the installation process for the developer's application.

Alternatively, the user can manually download and install the runtime before opening an AIR file. The developer can then distribute an AIR file by different means (for instance, via e-mail or an HTML link on a website). When the AIR file is opened, the runtime begins to process the application installation.

For more information on this process, see Distributing, Installing, and Running AIR applications

The AIR security model allows users to decide whether to install an AIR application. The AIR install experience provides several improvements over native application install technologies that make this trust decision easier for users:

• The runtime provides a consistent installation experience on all operating systems, even when an AIR application is installed from a link in a web browser. Most native application install experiences depend upon the browser or other application to provide security information, if it is provided at all.

• The AIR application install experience identifies the source of the application and information about what privileges are available to the application (if the user allows the installation to proceed).

• The runtime administers the installation process of an AIR application. An AIR application cannot manipulate the installation process the runtime uses.

In general, users should not install any desktop application that comes from a source that they do not trust, or that cannot be verified. The burden of proof on security for native applications is equally true for AIR applications as it is for other installable applications.

The installation directory can be set using one of the following two options:

1. The user customizes the destination during installation. The application installs to wherever the user specifies.

2. If the user does not change the install destination, the application installs to the default path as determined by the runtime:

   • Mac OS: ~/Applications/

   • Windows XP and earlier: C:\Program Files\

   • Windows Vista: ~/Apps/

   • Linux: /opt/

   If the developer specifies an installFolder setting in the application descriptor file, the application is installed to a subpath of this directory.

The install process for AIR applications copies all files that the developer has included within the AIR installer file onto the user's local computer. The installed application is composed of:

• Windows: A directory containing all files included in the AIR installer file. The runtime also creates an exe file during the installation of the AIR application.

• Linux: A directory containing all files included in the AIR installer file. The runtime also creates a bin file during the installation of the AIR application.

• Mac OS: An app file that contains all of the contents of the AIR installer file. It can be inspected using the "Show Package Contents" option in Finder. The runtime creates this app file as part of the installation of the AIR application.

An AIR application is run by:

• Windows: Running the .exe file in the install folder, or a shortcut that corresponds to this file (such as a shortcut on the Start Menu or desktop).

• Linux: Launching the .bin file in the install folder, choosing the application from the Applications menu, or running from an alias or desktop shortcut.

• Mac OS: Running the .app file or an alias that points to it.

The application file system also includes subdirectories related to the function of the application. For example, information written to encrypted local storage is saved to a subdirectory in a directory named after the application identifier of the application.

AIR applications have privileges to write to any location on the user's hard drive; however, developers are encouraged to use the app-storage:/ path for local storage related to their application. Files written to app-storage:/ from an application are located in a standard location depending on the user's operating system:

• On Mac OS: the storage directory of an application is <appData>/<appId>/Local Store/ where <appData> is the user's “preferences folder,” typically: /Users/<user>/Library/Preferences

• On Windows: the storage directory of an application is <appData>\<appId>\Local Store\ where <appData> is the user's CSIDL_APPDATA “Special Folder,” typically: C:\Documents and Settings\<user>\Application Data

• On Linux: <appData>/<appID>/Local Store/where <appData> is /home/<user>/.appdata

You can access the application storage directory via the air.File.applicationStorageDirectory property. You can access its contents using the resolvePath() method of the File class. For details, see Working with the file system.

When the user installs an AIR application that requires an updated version of the runtime, the runtime automatically installs the required runtime update.

To update the runtime, a user must have administrative privileges for the computer.

Development and deployment of software updates are one of the biggest security challenges facing native code applications. The AIR API provides a mechanism to improve this: the Updater.update() method can be invoked upon launch to check a remote location for an AIR file. If an update is appropriate, the AIR file is downloaded, installed, and the application restarts. Developers can use this class not only to provide new functionality but also respond to potential security vulnerabilities.

A user can uninstall an AIR application:

• On Windows: Using the Add/Remove Programs panel to remove the application.

• On Mac OS: Deleting the app file from the install location.

Removing an AIR application removes all files in the application directory. However, it does not remove files that the application may have written to outside of the application directory. Removing AIR applications does not revert changes the AIR application has made to files outside of the application directory.

AIR can be uninstalled:

• On Windows: by running Add/Remove Programs from the Control Panel, selecting Adobe AIR and selecting “Remove”.

• On Mac OS: by running the Adobe AIR Uninstaller application in the Applications directory.

On Windows, administrators can configure a machine to prevent (or allow) AIR application installation and runtime updates. These settings are contained in the Windows registry under the following key: HKLM\Software\Policies\Adobe\AIR. They include the following: