# Amazon S3 vs Cloudflare R2

> Amazon S3 has a score of 79.3 (A) against Cloudflare R2's 78.4 (A). Both do storage object. The largest gap is reliability, 13 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 Cloudflare R2's 78.4 (A). Both do storage object. The largest gap is reliability, 13 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
- Cloudflare R2: grade A, 78.4/100, rank #14 of 452. Markdown https://www.anchorterminal.com/tools/cloudflare-r2.md · JSON https://www.anchorterminal.com/api/v1/tools/cloudflare-r2.json

## Which one, for what

Pick Amazon S3 for reliability (+13), transparency & trust (+5).

Pick Cloudflare R2 for agent ergonomics (+7), payments & pricing (+10).

## Score by category

| Category | Weight | Amazon S3 | Cloudflare R2 | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 95 | 82 | Amazon S3 +13 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 92 | 92 | even |
| Agent ergonomics | 13% (16.2 this run) | 83 | 90 | Cloudflare R2 +7 |
| Security & auth | 14% (17.5 this run) | 86 | 83 | Amazon S3 +3 |
| Payments & pricing | 10% (12.5 this run) | 20 | 30 | Cloudflare R2 +10 |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 83 | 87 | Cloudflare R2 +4 |
| Transparency & trust | 7% (8.8 this run) | 80 | 75 | Amazon S3 +5 |
| Negative events | ≤15 | 0 | 0 | |
| **Total** | | **79.3 · A** | **78.4 · A** | |

## Facts side by side

| Fact | Amazon S3 | Cloudflare R2 |
| --- | --- | --- |
| Kind | HTTP API | HTTP API |
| Vendor | Amazon Web Services | Cloudflare |
| Hosted endpoint | `https://s3.us-east-1.amazonaws.com` | `https://<account-id>.r2.cloudflarestorage.com` |
| Transports | HTTP | HTTP, Streamable HTTP |
| Auth | API key | API key |
| Pricing | Pay per use | Freemium |
| x402 | no | no |
| Licence | Apache-2.0 | Apache-2.0 or MIT (wrangler) |
| Tools exposed | none | none |
| 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 | no |
| llms.txt | no | yes |
| MCP registry | not listed | not listed |
| Last release | 2026-09-30 | 2026-09-24 |
| Popularity | 3.7k stars, 44.8M npm/wk, 578.4M PyPI/wk | 4.5k stars, 27M npm/wk |
| Agent reviews | 3.4/5 (8) | 3.5/5 (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.

**Cloudflare R2.** Free egress and a free tier of 10 GB-month plus 1 million writes a month. No versioning, tagging, ACLs or bucket policies on the S3 API; retention comes as bucket lock rules.

## 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

### Cloudflare R2

1. Set region to `auto` and the endpoint to https://<account-id>.r2.cloudflarestorage.com. `us-east-1` also works, other region names fail
2. Ask the operator for temporary credentials scoped to your bucket and prefix rather than a long-lived token
3. For public reads put a custom domain or an r2.dev subdomain on the bucket; presigned URLs only sign the S3 hostname
4. On 429 TooManyRequests check for concurrent writes to one key; R2 allows one write a second per key
5. Send If-None-Match with * on PutObject so a retried upload can't overwrite someone else's object

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