"401 - bad_auth_token" Backblaze B2 Cloud Storage


I’m running Duplicati on Windows 10 to manage my backups to Backblaze B2 Cloud Storage. For the most part, it works great, but sometimes I get failed backups with the error “401 Invalid authorization token” being given. This is not every time. I’m still trying to narrow down the circumstances as to when/why this is happening. Here’s what I suspect:

I use Duplicati to perform 3 separate backup tasks running from a single desktop computer to backup different data sources. All data is being backed up to Backblaze B2 Cloud Storage, but to different buckets. Each of my backups are scheduled to run 4 hours apart from one another every evening. My understanding through reading the documentation, is that Duplicati tries to use any existing, open connection to Backblaze B2 each time it runs. A Backblaze knowledge base article found here: b2_get_upload_url talks about a 24 hour period that the auth token lives before expiring. I don’t have any detailed knowledge of how the handshake/authentication process works between Duplicati and Backblaze B2 Cloud Storage, but it seems (based off the error) that an incorrect auth token is being offered and subsequently rejected.

What I’ve learned:
If I leave it alone for a few days and then initiate a manual run of a particular backup, it often works. If shortly after the backup is successful I try to manually run a different backup task (also to backblaze, seperate bucket) I get the bad auth token error. It seems I have to leave it alone for a day or two to allow for what I suspect is some type of token expiration before it will work again.

Anyone have any similar problems backing up to Backblaze B2 Cloud Storage from a Windows 10 computer? Any ideas as to how to go about troubleshooting this? Any help would be appreciated. So far, I’m loving Duplicati, just have this one thing nagging at me.




Bump. Anyone using Duplicati with Backblaze B2???



I target B2 on numerous systems… Windows 10, Linux, Synology… have never had this problem!


This seems like a Duplicati issue. Backblaze returns an ‘expired’ message in the error string (if the token is expired), and Duplicati can fetch a new token – which seems like standard error handling for a rejected token regardless. Ideally, an error would only bubble up to the user in the case that getting a new token itself fails.


Is there any more detail about the error in the logs (click on the line with the timestamp to get more info)?

In the job logs, be sure to check the “Remote” tab as that should include all the calls to your destination.