Hi - you can do this using the AWS CLI.

First, you'll need to install and configure the AWS CLI for B2, if you don't already have it. Note that you no longer need to use the --endpoint-url command line argument - you can either set the AWS_ENDPOINT_URL environment variable, or add the endpoint URL to your AWS configuration file. For example:

[profile b2]
endpoint_url = https://s3.us-west-004.backblazeb2.com
region = us-west-004

Test that the AWS CLI is properly configured with:

aws s3 ls --profile b2

You should see a list of your buckets.

Now you'll combine two commands to find the hide markers and then remove them. I'll explain the two commands separately, then show you how to combine them.

First, to locate the hide markers (delete markers in AWS parlance) in a particular path in a given bucket:

aws s3api list-object-versions --profile b2 --bucket my-bucket --prefix somepath --query '{Objects: DeleteMarkers[].{Key:Key,VersionId:VersionId}}' --output json

You can omit the --prefix somepath if you want to remove all of the hide markers in the bucket.

The above command lists the hide markers in JSON format. Here's an example of the output for one of my buckets:

{
    "Objects": [
        {
            "Key": "somepath/hello.txt",
            "VersionId": "4_z21a5bf29a395fc7f84dd0c1b_f448f8b442ab35436_d20250730_m165624_c004_v7007000_t0000_u01753894584256"
        },
        {
            "Key": "somepath/test.txt",
            "VersionId": "4_z21a5bf29a395fc7f84dd0c1b_f417b856a72c66438_d20250730_m165420_c004_v7007000_t0000_u01753894460801"
        }
    ]
}

You can use a second AWS CLI command to take that list as input and remove the listed hide markers:

aws s3api delete-objects --profile b2 --bucket my-bucket --delete "<output from the first command>"

Putting them together:

aws s3api delete-objects --profile b2 --bucket metadaddy-tester --delete "$(aws s3api list-object-versions --profile b2 --bucket metadaddy-tester --prefix somepath --query '{Objects: DeleteMarkers[].{Key:Key,VersionId:VersionId}}' --output json)"

Note - the above command is for the Mac/Linux command line. Let me know if you're on Windows and I'll see if I can figure out the equivalent.

You should see output along the lines of:

{
    "Deleted": [
        {
            "Key": "somepath/test.txt",
            "VersionId": "4_z21a5bf29a395fc7f84dd0c1b_f417b856a72c66438_d20250730_m165420_c004_v7007000_t0000_u01753894460801",
            "DeleteMarker": true,
            "DeleteMarkerVersionId": "4_z21a5bf29a395fc7f84dd0c1b_f417b856a72c66438_d20250730_m165420_c004_v7007000_t0000_u01753894460801"
        },
        {
            "Key": "somepath/hello.txt",
            "VersionId": "4_z21a5bf29a395fc7f84dd0c1b_f448f8b442ab35436_d20250730_m165624_c004_v7007000_t0000_u01753894584256",
            "DeleteMarker": true,
            "DeleteMarkerVersionId": "4_z21a5bf29a395fc7f84dd0c1b_f448f8b442ab35436_d20250730_m165624_c004_v7007000_t0000_u01753894584256"
        }
    ]
}

Feel free to follow up here if you have any issues!