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ERROR_FORMS_AUTH_REQUIRED
Interactive web authentication is required
ERROR_FORMS_AUTH_REQUIRED is a Win32 result associated with WebDAV or document access backed by forms authentication. When ERROR_FORMS_AUTH_REQUIRED is returned, diagnosis should begin with the exact API, target object, and operation that produced it rather than with the message text alone.
What the result means
The remote location requires an interactive forms-based sign-in before file access can continue. For ERROR_FORMS_AUTH_REQUIRED, the practical meaning depends on the caller and on whether the affected object is local, remote, removable, policy-managed, or handled asynchronously. Diagnostics for ERROR_FORMS_AUTH_REQUIRED should retain its symbolic name, numeric value, and the operation name together.
What to check
- Open the service in an interactive browser and complete the required sign-in.
- Confirm that the site is trusted according to the organization’s policy.
- Check whether the application supports modern authentication instead of relying on browser session state.
- Avoid embedding user passwords in scripts or command lines.
Recommended handling
For unattended software, use a supported token or service authentication flow. A background process generally cannot satisfy an interactive forms challenge reliably.
Developer notes
Code handling ERROR_FORMS_AUTH_REQUIRED should capture the failing API, resolved path or device identity, requested access, process identity, and the first observed error. After a call that reports ERROR_FORMS_AUTH_REQUIRED, read GetLastError() immediately because later cleanup or logging can overwrite the value. Retry ERROR_FORMS_AUTH_REQUIRED only when the specific condition is documented as transient, using a bounded delay and cancellation support.
References
- Microsoft: System error codes relevant to ERROR_FORMS_AUTH_REQUIRED
- Microsoft: File management context for ERROR_FORMS_AUTH_REQUIRED
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