About the HTML environment

Adobe AIR 1.0 and later

Adobe® AIR® uses WebKit (www.webkit.org), also used by the Safari web browser, to parse, layout, and render HTML and JavaScript content. Using the AIR APIs in HTML content is optional. You can program in the content of an HTMLLoader object or HTML window entirely with HTML and JavaScript. Most existing HTML pages and applications should run with few changes (assuming they use HTML, CSS, DOM, and JavaScript features compatible with WebKit).

Important: New versions of the Adobe AIR runtime may include updated versions of WebKit. A WebKit update in a new version of AIR may result in unexpected changes in a deployed AIR application. These changes may affect the behavior or appearance of HTML content in an application. For example, improvements or corrections in WebKit rendering may change the layout of elements in an application’s user interface. For this reason, it is highly recommended that you provide an update mechanism in your application. Should you need to update your application due to a change in the WebKit version included in AIR, the AIR update mechanism can prompt the user to install the new version of your application.

The following table lists the version of the Safari web browser that uses the version of WebKit equivalent to that used in AIR:

AIR version

Safari version






4.0 Beta











You can always determine the installed version of WebKit by examining the default user agent string returned by a HTMLLoader object:

var htmlLoader:HTMLLoader = new HTMLLoader(); 
trace( htmlLoader.userAgent );

Keep in mind that the version of WebKit used in AIR is not identical to the open source version. Some features are not supported in AIR and the AIR version can include security and bug fixes not yet available in the corresponding WebKit version. See WebKit features not supported in AIR.

Because AIR applications run directly on the desktop, with full access to the file system, the security model for HTML content is more stringent than the security model of a typical web browser. In AIR, only content loaded from the application installation directory is placed in the application sandbox. The application sandbox has the highest level of privilege and allows access to the AIR APIs. AIR places other content into isolated sandboxes based on where that content came from. Files loaded from the file system go into a local sandbox. Files loaded from the network using the http: or https: protocols go into a sandbox based on the domain of the remote server. Content in these non-application sandboxes is prohibited from accessing any AIR API and runs much as it would in a typical web browser.

HTML content in AIR does not display SWF or PDF content if alpha, scaling, or transparency settings are applied. For more information, see Considerations when loading SWF or PDF content in an HTML page and Window transparency.