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When you load an Office Add-in from https://localhost or when you use Fiddler, you receive the following error:
We can't open this add-in from localhost.
One cause of this error is that the Microsoft Edge Web Viewer does not have a loopback exemption. To resolve this issue, use either of these options to add a local loopback exemption to Desktop App Web Viewer:
CheckNetIsolation LoopbackExempt -a -n="microsoft.win32webviewhost_cw5n1h2txyewy"
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Microsoft provides third-party contact information to help you find technical support. This contact information may change without notice. Microsoft does not guarantee the accuracy of this third-party contact information.
Ask Learn is an AI assistant that can answer questions, clarify concepts, and define terms using trusted Microsoft documentation.
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