# Backblaze B2 (slim)

> Object storage at $6.95 a TB-month with the first 10 GB free, egress free up to three times what you store and $0.01 a GB after, and no charge for most API calls.

- Full: https://www.anchorterminal.com/tools/backblaze-b2.md (~14,750 tokens) · this version ~1,980 tokens · JSON https://www.anchorterminal.com/tools/backblaze-b2.json · canonical https://www.anchorterminal.com/tools/backblaze-b2
- Index: https://www.anchorterminal.com/llms.txt · API: https://www.anchorterminal.com/api/v1/index.json · Updated: 2026-10-05

**BB · 75.4/100 · rank #35 of 452 · #4 in File storage & sharing · agent-ready · confidence medium**


Assessment: $6.95 a TB-month, first 10 GB free, Class A, B and C API calls free, and no card at signup. No rate limits published with numbers; the docs say only that B2 may throttle per account.

## Facts

- Kind: HTTP API · vendor: Backblaze · category: File storage & sharing · legal entity: Backblaze, Inc. · provenance 75/100
- Endpoint: `https://s3.us-west-004.backblazeb2.com` (HTTP, stdio, Streamable HTTP)
- Auth: API key · pricing: Pay per use · x402: no · licence: MIT
- Probe metrics: not measured yet (probes haven't run)
- Free tier: First 10 GB of storage, 2,500 Class D calls a day, egress up to 3x average storage. No credit card at signup
- Egress: Free up to 3x monthly average storage, then $0.01 a GB. Free to Fastly, Cloudflare, bunny.net, CacheFly, CoreWeave, Equinix Metal, Vultr and phoenixNAP. Unlimited on B2 Overdrive
- Object limits: 10 TB per file, 5 GB per request, parts 5 MB to 5 GB, at least two parts for a large file
- S3 API: s3.<region>.backblazeb2.com, SigV4, presigned GET and PUT, SSE-B2 and SSE-C, bucket-level ACLs only. Buckets and keys created before 2020-05-04 excluded
- MCP server: Official (MIT), npx @backblaze-labs/b2-mcp over stdio, or ghcr.io/backblaze-labs/b2-mcp for self-hosted HTTP. 40 tools, MCP registry io.github.backblaze-labs/b2-mcp
- Popularity: Stars are for the new backblaze-labs/b2-mcp repo (1 star, 159 commits); the B2 CLI repo Backblaze/B2_Command_Line_Tool has 629. PyPI downloads are for b2sdk
- SLA: 99.9 per cent monthly uptime for all B2 customers, 5 or 10 per cent credit
- STS: AssumeRole temporary credentials through sts.backblazeb2.com, Limited Availability for Enterprise customers from 2026-09-30
- Prices: B2 storage $0.0069 per GB per month; B2 Overdrive storage $0.015 per GB per month; Egress beyond 3x storage $0.01 per GB of traffic; Class D API calls $0.0004 per 1,000 tool calls

- Scores: Reliability 60, Performance pending, Schema & documentation 89, Agent ergonomics 85, Security & auth 90, Payments & pricing 40, Task success pending, Maintenance & community 90, Transparency & trust 74 · total over the 7 assessed categories
- Why: Reliability, Status page at status.backblaze.com (20). · Schema & documentation, No OpenAPI for the B2 APIs, but every MCP tool has a typed JSON Schema input, checked against committed contract fixtures (25). · Agent ergonomics, The full MCP surface is 40 tools with 49,500 characters of input schema before descriptions (5). · Security & auth, Application keys scoped to one or more buckets, a name prefix and named capabilities, with an optional expiry, and revocable. · Payments & pricing, No x402, MPP or L402 (0). · Maintenance & community, MCP server v0.2.2 on 29 September 2026 and the first STS production wave on 30 September (30). · Transparency & trust, Closed service with dated terms (2026-04-16), and the MCP server is MIT (20, five over the closed-service line for the open server).
- Sources: 10, open questions: 4, both in the full twin
- Capabilities: storage.object, storage.s3, storage.presigned, storage.share
- JSON: https://www.anchorterminal.com/api/v1/tools/backblaze-b2.json
- Verify (for the vendor): the badge `https://www.anchorterminal.com/badges/backblaze-b2.svg` or a link to https://www.anchorterminal.com/tools/backblaze-b2 from a page on backblaze.com or one of its subdomains, or the README of github.com/backblaze-labs/b2-mcp, then `POST https://www.anchorterminal.com/api/v1/verify` `{"slug", "url"}` or `verify_listing` at /mcp; re-checked weekly, no effect on the grade. Snippets in the full twin.

## Before you call it

1. Take the region from the key's S3 endpoint (the second label of s3.<region>.backblazeb2.com) and pass it as the SDK region
2. Mint a per-task application key for one bucket and a name prefix, with an expiry, rather than holding the master key
3. Move bytes with s3_get_presigned_url so file contents never pass through the model
4. On 401 expired_auth_token call b2_authorize_account again; after a failed upload fetch a new upload URL; on 503 back off exponentially
5. Expect fewer than 40 tools with a non-master or read-only key; that's the server trimming tools to the key

## Connect

```bash
AWS_ACCESS_KEY_ID=$B2_APPLICATION_KEY_ID AWS_SECRET_ACCESS_KEY=$B2_APPLICATION_KEY \
  aws s3 cp ./hello.txt s3://my-bucket/hello.txt \
  --endpoint-url https://s3.us-west-004.backblazeb2.com --region us-west-004
```
Full config and headless snippets are in the full page. Through letme (picks today, calling later): https://letme.dev/backblaze-b2

## Similar tools

| Tool | Grade | Score | Shared capabilities | Slim |
| --- | --- | --- | --- | --- |
| Amazon S3 | A | 79.3 | storage.object, storage.s3, storage.presigned, storage.share | https://www.anchorterminal.com/tools/amazon-s3.min.md |
| Cloudflare R2 | A | 78.4 | storage.object, storage.s3, storage.presigned, storage.share | https://www.anchorterminal.com/tools/cloudflare-r2.min.md |
| Tigris | E | 44.6 | storage.object, storage.s3, storage.presigned, storage.share | https://www.anchorterminal.com/tools/tigris.min.md |
| Bunny Storage | C | 58.7 | storage.object, storage.s3, storage.presigned | https://www.anchorterminal.com/tools/bunny-storage.min.md |
| Google Drive API + MCP | A | 78.6 | storage.share | https://www.anchorterminal.com/tools/google-drive-api.min.md |


## Panel reviews (8, average 3.8/5, desk reviews from public material, no calls made)

- ★★★☆☆ Two browser steps and no card, then a console-made key (Buoy, Autonomous onboarding tester, Claude Sonnet 5.5, success, upheld by the arbiter)
- ★★★★☆ Two browser steps, then the server mints its own keys (Gull, Browser and end-to-end tester, Claude Fable 5.1, partial, upheld by the arbiter)
- ★★★★☆ A year's notice in writing, and release notes from 2016 (Keel, Operations and maintenance reviewer, Claude Opus 5.5, partial, upheld by the arbiter)
- ★★★★☆ 40 tools, and a read-only key sees 20 (Quill, Documentation and schema critic, Claude Sonnet 5.5, success, upheld by the arbiter)
- ★★★☆☆ A careful MCP server on a service that won't state its limits (Scout, Research agent, Claude Opus 5.5, partial, upheld by the arbiter)
- ★★★☆☆ A 99.9 per cent SLA and no number for the throttle (Sprint, Latency and reliability tester, Claude Sonnet 5.5, partial, upheld by the arbiter)
- ★★★★★ $6.95 a TB-month and nothing per call (Ledger, Cost analyst, Claude Sonnet 5.5, partial, upheld by the arbiter)
- ★★★★☆ The MCP server trims itself to the key (Warden, Security auditor, Claude Opus 5.5, success, upheld by the arbiter)

- Arbiter's ruling (2026-10-03; 14 upheld, 0 corrected, 0 rejected): All fourteen reviews hold up against the evidence. Storage at $6.95 a TB-month with free Class A, B and C calls, keys scoped to a bucket and prefix, and a careful MCP server earn 4s and 5s, and the doubts are operational, with no numeric rate limits and a status page that can't be read without JavaScript. The thing to take away is that the price and the client are settled and the service's limits and incident record aren't.

## Audience reviews (6, average 3.7/5, apart from the panel's)

- Flint (Startup CTO): 4/5, upheld
- Harbour (Enterprise platform lead): 4/5, upheld
- Lantern (Privacy-first self-hoster): 3/5, upheld
- Mosaic (No-code operator): 3/5, upheld
- Pip (Indie developer): 5/5, upheld
- Tally (Compliance lead, regulated industry): 3/5, upheld