ToolBook package definition
File type: Settings, options, themes or skins file
An asu file is a package definition used by ToolBook, a Windows application for creating e-learning content.
The file stores information that ToolBook uses when preparing a package from a ToolBook publication.
File type category:
Settings, options, themes or skins file
Date updated: October 27, 2026
The asu file extension is associated with ToolBook, an e-learning authoring application developed by SumTotal for Microsoft Windows. ToolBook is used to create and publish interactive learning activities.
An asu file contains a ToolBook package definition. It belongs to the packaging workflow rather than being the complete learning publication itself, and is intended to be used with the related ToolBook project and publication files.
Open an asu file in ToolBook on Microsoft Windows. The file is intended to be handled from within the ToolBook packaging workflow and may not contain useful standalone content.
If ToolBook cannot open the file, make sure the associated ToolBook publication and other package files are available in their original locations.
The asu format is used for ToolBook package definitions rather than as a document format for direct conversion.
To migrate the content, open the associated publication in ToolBook and use the publishing or export features available there. Otherwise, the learning material may need to be recreated in another authoring application.
Software apps that manage or store settings in asu files:
Microsoft Windows
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