Connect Backblaze B2 with Blob0

Connect Blob0 to an existing Backblaze B2 bucket through its S3-compatible API. Match the bucket region and endpoint, use a manually created application key, and check its capabilities.

Use this guide for an existing Backblaze B2 Cloud Storage bucket. Blob0 connects through B2’s S3-compatible API; it is an object client, not Backblaze Computer Backup.

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Before you connect

Have an existing B2 bucket and its bucket-specific endpoint and Region. Get an application-key pair scoped to that bucket and the actions you need; the key must be allowed to list the bucket root for Test connection.
Leave the optional Public / custom domain field blank unless a direct-link domain has already been configured. See Provider configuration notes below for B2 key mapping and capability details.

Provider configuration notes

Copy the regional S3 endpoint and region from the bucket details in B2. For example, a bucket in us-west-004 uses https://s3.us-west-004.backblazeb2.com; use the values shown for your own bucket.

Match the bucket’s regional endpoint: Use the endpoint and region from this B2 bucket’s details. The us-west-004 example is https://s3.us-west-004.backblazeb2.com; do not reuse it for buckets in other regions. Enter the bucket name separately.
Create an S3-compatible application key: Create an application key manually. Map its keyID to Access Key ID and its applicationKey to Secret Access Key. Backblaze’s automatically created master app key cannot authenticate to the S3-compatible API.
Allow listing the bucket root: Use an application key that can list the selected bucket’s root. B2 requires listing requests to include a matching prefix when a key has a file name prefix restriction. Blob0 tests the connection with an empty prefix and has no starting-prefix field, so such a restriction can cause AccessDenied even when the key can access files under its allowed prefix.
Grant only the needed B2 capabilities: listFiles lists objects, readFiles reads and downloads, and writeFiles uploads; B2 maps Copy Object to both readFiles and writeFiles, so rename or move workflows may need both. Delete by name requires writeFiles and deleting a specific version requires deleteFiles; Backblaze generally recommends both for Delete Object workflows. Blob0 deletes by object key without a version ID, so it does not delete a selected historical version.
Keep bucket discovery scoped: Backblaze recommends enabling listAllBucketNames for bucket-restricted application keys when SDKs or integrations call ListBuckets. It exposes bucket names, not object access to other buckets. Blob0 asks for a specific bucket and does not show every bucket in the account; if region probing or permissions fail, check Backblaze’s capability map for ListBuckets and HeadBucket.

B2 application-key capabilities are not a promise of full AWS IAM or ACL compatibility. Blob0 works with the S3-compatible object operations supported by B2 and the key you provide.

Provider-specific limits

Blob0 is an S3-compatible object client, not Backblaze Computer Backup and not an AWS account console. B2 documents a defined S3-compatible API surface; do not assume every AWS IAM or ACL feature applies.
A B2 S3 delete by object name adds a delete marker. Blob0 sends the object key without a version ID, so deleting from the current list does not remove a selected historical version or clear version history; manage versions and lifecycle rules in B2.
Blob0 connects to the bucket you specify; it does not list or administer every bucket in the Backblaze account.

Fill in the Blob0 connection form

On first launch, use the connection form. To add another bucket later, open Settings → Connections → Add connection. Choose Backblaze B2 under Provider, then enter the bucket-specific endpoint, region and application-key pair.

Fill in the Blob0 connection form
App field	What to enter
Provider	Backblaze B2
Connection name	A local label, such as B2 archive. It does not rename the bucket.
S3 API endpoint	The regional endpoint in the bucket details. Example: https://s3.us-west-004.backblazeb2.com.
Bucket	The exact existing B2 bucket name, without a URL or folder prefix.
Region	The bucket region, such as us-west-004 for the endpoint example above.
Access Key ID	The application key ID (keyID), not the master key ID.
Secret Access Key	The matching application key (applicationKey), not the master app key.
Public / custom domain	Optional. Leave blank for private access; it does not authenticate the S3 connection.

Blob0 connection form with fictional settings: Connect Backblaze B2 with Blob0 — Real application interface with fictional settings; no usable credentials are shown.

Test and save the connection

Test connection
Select Test connection. Blob0 lists the selected bucket at its root and may show 0 items for an empty bucket. A successful result confirms only that this listing request succeeded; it does not prove access to object contents or permission to upload, overwrite, or delete.
The B2 connection test lists the selected bucket root with an empty prefix. If the application key is restricted to a file-name prefix, B2 may reject this listing even when objects under that prefix are accessible.
Add connection
After the test succeeds, select Add connection to save the profile and connect. Blob0 stores access keys in the macOS Keychain; the profile keeps non-sensitive connection details.

Optional: verify an authorized transfer

Only if the bucket owner has authorized write testing, upload a tiny temporary file under a new test name, download it and compare its contents, then delete that exact test object. Check the bucket policy and retention rules first; never use an existing object as the test file.

Troubleshooting

AccessDenied: Use a manually created application key, not the master app key. Confirm it has listFiles access for the bucket root; a file-name prefix restriction can conflict with the empty-prefix test.
SignatureDoesNotMatch: Check the pair mapping: keyID goes in Access Key ID and applicationKey goes in Secret Access Key. Then verify the bucket’s regional endpoint and Region.
NoSuchBucket or 404: Check the exact bucket name and use the regional endpoint from that bucket’s details. Do not carry an endpoint over from a bucket in another region.
Listing works but an operation is denied: Grant only the B2 capabilities needed: listFiles for listing, readFiles for reading and downloads, and writeFiles for uploads. Copy operations used by rename or move can require both readFiles and writeFiles.
Delete or historical versions: B2 S3 deletion by object name adds a delete marker. Blob0 does not select a version ID; manage historical versions and lifecycle rules in Backblaze tools.

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