Connect Backblaze B2 to Dropbucket (setup guide)

Backblaze B2 is low-cost storage that speaks the S3 API, so it works with Dropbucket out of the box. Backblaze includes a free download allowance tied to how much you store. Check their pricing page for the current terms before you plan on large downloads.

This guide takes about ten minutes.

What you need

A Backblaze account with B2 Cloud Storage turned on.
A Dropbucket account. The free plan works with B2.

Step 1: Create a bucket

Sign in to Backblaze. Under B2 Cloud Storage, open Buckets and click Create a Bucket.
Enter a name. Use lowercase letters, numbers and dashes, for example agency-transfers. Dropbucket won’t accept capitals or underscores.
Keep the bucket Private. Dropbucket uses short-lived signed links, so the bucket never needs to be public.
Create the bucket.

The bucket page shows an Endpoint, for example s3.us-west-004.backblazeb2.com. Copy it. The middle part (us-west-004) is your region.

B2 keeps old versions of a file by default. Dropbucket doesn’t overwrite files, so this rarely matters, but you can add a lifecycle rule in Backblaze to keep only the latest version if you like.

Step 2: Create an application key

The master application key doesn’t work with the S3 API. You need a separate key.

Open Application Keys and click Add a New Application Key.
Name of Key: something like dropbucket.
Allow access to Bucket(s): choose the bucket from Step 1.
Type of Access: Read and Write.
Leave File name prefix and Duration blank. A key with a duration stops working when it expires, and your links stop with it.
Click Create New Key.

Backblaze shows a keyID and an applicationKey. Copy both. The application key is shown once only.

The exact menu may differ slightly as Backblaze updates its console.

Step 3: Add the CORS rule

Files travel from your client’s browser straight into B2. The browser only allows that if the bucket says Dropbucket’s pages may upload to it. That permission is a CORS rule, and on B2 it has to apply to the S3 Compatible API.

A key limited to one bucket isn’t allowed to change bucket settings, so Dropbucket usually can’t add this rule for you on B2. Set it once yourself. There are two ways.

Option A: the Backblaze web console

On the Buckets page, click CORS Rules under your bucket.
Choose Share everything in this bucket with this one origin and enter https://app.dropbucket.io.
Under Apply CORS rules to the following APIs, choose S3 Compatible API or Both. A rule for the B2 Native API only won’t help.
Click Update CORS Rules. Give it a minute to apply.

The web console only takes one origin. If you also use your own domain for download and upload pages, use Option B.

Option B: the B2 command-line tool

Install the B2 command-line tool and sign in with b2 account authorize (your master key is fine here, because this is the B2 tool, not the S3 API).

Save this as cors.json:

[
  {
    "corsRuleName": "dropbucket-uploads",
    "allowedOrigins": [
      "https://app.dropbucket.io"
    ],
    "allowedOperations": [
      "s3_get",
      "s3_put",
      "s3_head"
    ],
    "allowedHeaders": [
      "*"
    ],
    "exposeHeaders": [
      "ETag"
    ],
    "maxAgeSeconds": 3600
  }
]

Then run:

b2 bucket update --cors-rules "$(<cors.json)" agency-transfers allPrivate

Use your own bucket name in place of agency-transfers. If you have a custom domain such as files.youragency.com, add "https://files.youragency.com" to allowedOrigins, with a comma after the first entry. See Put your download pages on your own domain.

This is the same rule Dropbucket shows on its Storage page, written in B2’s own format. The Storage page version (with AllowedOrigins, AllowedMethods and so on) is the S3 format, which B2 also accepts through the S3 API. Either way, keep ETag exposed. Dropbucket reads it after every chunk of a large upload.

Step 4: Connect B2 in Dropbucket

In Dropbucket, go to Settings → Storage.
Under Provider, choose Backblaze B2.
Endpoint: the endpoint from Step 1 with https:// in front, for example https://s3.us-west-004.backblazeb2.com.
Bucket: the bucket name.
Region: the middle part of the endpoint, for example us-west-004. Dropbucket fills in us-west-004 by default, so change it if yours is different.
Access key ID: the keyID. Secret access key: the applicationKey.
Folder inside the bucket (optional): leave blank, or enter a folder name like client-files.
Leave Path-style URLs ticked.

Copy the endpoint from the bucket page rather than guessing the number. us-west-002 and us-west-004 are different places.

Test the connection

Press Test and save.

Dropbucket writes a tiny test file, reads it back and deletes it. When that works, the Status card shows a tick next to Keys work.

It then tries to set the CORS rule and runs a real upload from your browser. With a bucket-limited key you’ll probably see “We couldn’t set this automatically on your provider.” That’s expected. If you set the rule in Step 3, Browser uploads allowed (CORS) will tick over. If not, wait a minute and press Check again.

Troubleshooting

“The storage provider refused these keys.” You may have used the master application key, which the S3 API rejects. Create a separate key. Also check the key is Read and Write and covers this bucket.

“That bucket was not found at this endpoint.” Check the bucket name. If it’s right, the endpoint region is probably wrong. Copy it from the bucket page.

“Wrong region or endpoint for this bucket.” The Region field doesn’t match the endpoint. They should share the same us-west-004 style code.

Keys work, but the CORS check fails. The most common cause on B2 is a rule that applies to the B2 Native API only. Make sure it covers the S3 Compatible API. Also check the origin is exactly https://app.dropbucket.io with no trailing slash. If the web console rule doesn’t pass, use Option B.

“Your storage didn’t return an ETag.” The rule doesn’t expose the ETag header. Use Option B, which sets it explicitly.

Uploads fail with 403. Usually CORS. If CORS passes, check the key hasn’t been deleted or expired.

Path-style. Keep Path-style URLs ticked for B2.

Next steps

Add your logo under Settings → Branding, then send a transfer or create a request link so clients can upload straight into B2.

Ready to try it? Create a free Dropbucket account and connect your bucket.

Connect Backblaze B2 to Dropbucket