These files are used by QuickBooks web connector (QBWC), an application for Microsoft Windows that allows data to be exchanged between QuickBooks desktop applications and a web service.

These files are in XML format, and contain all the connection parameters to connect to the web service.

The .QWC files are usually downloaded from the web service provider website and then manually added to the QuickBooks application by clicking the 'Add Application' button and browsing to the .QWC file. QuickBooks will then attempt to establish a connection to the web service using the XML parameters within the web connector file.