Forum Discussion
Error when connecting with Azure Blob Storage container
1) What this Error actually means
> Malformed web response means Power BI called the Blob REST API, but the response it received was not what Power BI expected
This usually happens due to
* Authentication/token changes
* TLS / security enforcement changes
* Storage account configuration changes
* Container-level access changes
* API throttling or partial outage
2) Most common causes
>Access level changed on the Container
If the container was:
* Public → Private
* Or access policy modified
Power BI can no longer list files.
Check in Azure Portal
* Storage Account → Containers
* Verify Public access level
* If using SAS → check expiry
This is the cause in long-running setups.
>SAS Token Expired
If your connection uses a SAS token, they often
* Expire after 6–12 months
* Are silently rotated by security teams
Symptoms
* Worked fine historically
* Suddenly fails without model changes
Fix
* Generate a new SAS token
* Update Power BI connection
* Republish dataset
> TLS / Security Policy Update
Microsoft recently enforced stricter TLS and API behavior.
If
* Storage account enforces HTTPS-only
* Older Power BI Desktop or gateway is used
Actions
* Update Power BI Desktop
* Update On-Premises Data Gateway
This explains malformed response from a valid endpoint.
>Blob Endpoint now redirecting
Power BI does not like redirects in Blob REST calls.
Example
* Old endpoint → redirected to new region / firewall rule
* Private endpoint introduced
Check
* Networking → Firewalls & virtual networks
* Private endpoint enabled?
* IP restrictions changed?
>Temporary Azure Blob Service Issue
Less common, but possible.
Check
* Azure Service Health
* Any incident for Blob Storage / REST API
3) Quick diagnostics you can do now
Test in Power BI Desktop
1. Open Transform Data
2. Click Refresh Preview
3. If it fails → authentication issue
4. If it loads but service refresh fails → gateway/network issue
Clear & Re-enter Credentials
In Power BI Desktop
* File → Options → Data Source Settings
* Find Azure Blob
* Clear Permissions
* Reconnect
This fixes token corruption issues
Try Connecting via Folder instead of Container
If you are using
Azure Blob Storage
Azure Data Lake Storage Gen2
(or vice versa)
Some tenants enforce Gen2 behavior now.
4) If you need an emergency workaround
If refresh is business-critical and engineers are unavailable:
Option A Download file locally (Temporary)
* Download blob file manually
* Point Power BI to local copy
* Keep dashboard alive temporarily
Option B Use HTTPS URL + Web Connector (Short-term)
```text
https://<account>.blob.core.windows.net/<container>/<file>
Not ideal, but works for emergencies
A “malformed web response” from Azure Blob usually indicates an authentication, access policy, or security configuration change rather
than a Power BI issue, especially when the solution has worked historically.
Please give heads-up if this is helpful other let us know the issue. Thank you!
Common Causes and Fixes:
- Expired SAS Token or Credentials
- If your dashboard uses a SAS token or key embedded in the connection string, check if it has expired.
- Generate a new SAS token in the Azure Portal:
- Go to Storage Account → Containers → Generate SAS.
- Update the Power BI data source with the new token.
- Changes in Container Permissions
- Ensure the container still has List and Read permissions for the account or token you are using.
- If your engineers recently applied security hardening, the ?comp=list&restype=container call may fail without proper permissions.
- Malformed URL or Encoding
- The error mentions & which is HTML encoding for &. This usually happens if the URL was copied from an HTML page or incorrectly encoded.
- In Power BI, the URL should look like:
https://<storageaccount>.blob.core.windows.net/<container>?restype=container&comp=list&<SAS token>
Make sure there are no & in the actual connection string.
- Check Gateway or Network
- If you are using an on-premises gateway, verify that it can still reach *.blob.core.windows.net on port 443.
- Sometimes firewall rules or proxy changes block the request.
Quick Test:
- Open the URL in a browser (with the SAS token) and see if you get an XML listing of blobs.
- If you get an error there, the issue is on the Azure side (permissions or token).
- If it works, then the problem is in Power BI configuration or gateway.
Official Documentation:
Grant limited access to data with shared access signatures (SAS) - Azure Storage | Microsoft Learn
If this response was helpful in any way, I’d gladly accept a 👍much like the joy of seeing a DAX measure work first time without needing another FILTER.
Please mark it as the correct solution. It helps other community members find their way faster (and saves them from another endless loop 🌀.