Unknown Content Type Handling

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UCT System

The Unknown Content Type Handling System has the following components:

Unknown Content Type Handler

Handles navigations to content of unknown types in the rendering engine, determines what action to pursue (showing UI if necessary), downloading and opening the content. Should contain a means of registering special handling options for common content types. See more information here: UCT Handler

Helper Application Service

Determines how a file of a particular type (content type, extension) will be handled when downloaded, based on a combination of application overrides and system settings. Also tells how files of specific types are handled by the operating system (system defaults), regardless of any overrides specified in the application. See more information here: Helper Application Service


Downloads a file to disk, supporting interrupted connections. This is WebBrowserPersist.

Download Manager

Used by the UCT system to show user progress on a download transaction. See more information here: Download Manager


These components work together when content of an unknown type is navigated to over the web. The Helper Application Service and the Downloader can be used separately by other parts of the application that want to know about how files are handled locally or by the system, or to download files.