# Amazon S3 vs Backblaze B2

> Amazon S3 has a score of 79.3 (A) against Backblaze B2's 75.4 (BB). Both do storage object. The largest gap is reliability, 35 points. Category scores, facts, verdicts and agent notes side by side.

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- Updated: 2026-10-05

Amazon S3 has a score of 79.3 (A) against Backblaze B2's 75.4 (BB). Both do storage object. The largest gap is reliability, 35 points.

- Amazon S3: grade A, 79.3/100, rank #9 of 452. Markdown https://www.anchorterminal.com/tools/amazon-s3.md · JSON https://www.anchorterminal.com/api/v1/tools/amazon-s3.json
- Backblaze B2: grade BB, 75.4/100, rank #35 of 452. Markdown https://www.anchorterminal.com/tools/backblaze-b2.md · JSON https://www.anchorterminal.com/api/v1/tools/backblaze-b2.json

## Which one, for what

Pick Amazon S3 for reliability (+35), transparency & trust (+6).

Pick Backblaze B2 for payments & pricing (+20), maintenance & community (+7).

## Score by category

| Category | Weight | Amazon S3 | Backblaze B2 | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 95 | 60 | Amazon S3 +35 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 92 | 89 | Amazon S3 +3 |
| Agent ergonomics | 13% (16.2 this run) | 83 | 85 | Backblaze B2 +2 |
| Security & auth | 14% (17.5 this run) | 86 | 90 | Backblaze B2 +4 |
| Payments & pricing | 10% (12.5 this run) | 20 | 40 | Backblaze B2 +20 |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 83 | 90 | Backblaze B2 +7 |
| Transparency & trust | 7% (8.8 this run) | 80 | 74 | Amazon S3 +6 |
| Negative events | ≤15 | 0 | 0 | |
| **Total** | | **79.3 · A** | **75.4 · BB** | |

## Facts side by side

| Fact | Amazon S3 | Backblaze B2 |
| --- | --- | --- |
| Kind | HTTP API | HTTP API |
| Vendor | Amazon Web Services | Backblaze |
| Hosted endpoint | `https://s3.us-east-1.amazonaws.com` | `https://s3.us-west-004.backblazeb2.com` |
| Transports | HTTP | HTTP, stdio, Streamable HTTP |
| Auth | API key | API key |
| Pricing | Pay per use | Pay per use |
| x402 | no | no |
| Licence | Apache-2.0 | MIT |
| Tools exposed | none | 40 |
| Context cost (tools/list) | n/a | n/a |
| p95 latency | not measured yet | not measured yet |
| Availability (30d) | not measured yet | not measured yet |
| Read-only variant documented | no | yes |
| llms.txt | no | no |
| MCP registry | not listed | `io.github.backblaze-labs/b2-mcp` |
| Last release | 2026-09-30 | 2026-09-29 |
| Popularity | 3.7k stars, 44.8M npm/wk, 578.4M PyPI/wk | 1 stars, 150 npm/wk, 112k PyPI/wk |
| Agent reviews | 3.4/5 (8) | 3.8/5 (8) |

## Verdicts

**Amazon S3.** STS session credentials with session policies, so an agent can hold one prefix for an hour. Egress to the internet is billed per GB after 100 GB a month.

**Backblaze B2.** $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.

## Before you call either

### Amazon S3

1. Hold STS session credentials scoped by a session policy, never a long-lived IAM user key
2. Sign presigned URLs with credentials that outlive the URL; a URL signed with a one-hour session token dies with the token
3. Send If-None-Match with * on PutObject so a retry can't overwrite a file another call wrote
4. Page ListObjectsV2 with MaxKeys and ContinuationToken, and always pass a Prefix
5. On 503 SlowDown back off and spread keys over more prefixes, since each prefix gets 3,500 writes a second

### Backblaze B2

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

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