Comparison

AWS S3 vs Cloudflare R2 vs Backblaze B2

Object storage for AI agent workloads

Object storage is infrastructure agents touch constantly — storing retrieved data, serving assets, archiving outputs. The choice matters more than it looks: egress fees, SDK breadth, and auth complexity all affect how autonomously an agent can operate.

Highest AN Score

AWS S3

8.1/10

Execution
8.6
Access
7.2
Confidence
0.6
Tier
L4 Native

Cloudflare R2

7.4/10

Execution
7.6
Access
7
Confidence
0.55
Tier
L3 Ready

Backblaze B2

6.6/10

Execution
7
Access
5.8
Confidence
0.52
Tier
L3 Ready

The real question isn't "which is best" — it's "what do you read?"

If your agent reads more than it writes, R2 wins on total cost despite a lower AN Score. Egress is the hidden multiplier in storage economics. S3 charges $0.09/GB out; R2 charges $0. For an agent that reads 100GB/month, that's $9/month in invisible S3 fees. S3 wins on execution quality (8.6 vs 7.6) and ecosystem breadth, but R2's cost advantage compounds over time.

AWS S3 8.1/10

The default choice when you need maximum reliability and ecosystem breadth.

Strengths

  • + Near-universal SDK support — every language, every framework, every agent runtime
  • + Pre-signed URLs enable secure, time-limited access without exposing credentials
  • + Deep integration with 200+ AWS services (Lambda triggers, CloudFront CDN, Athena queries)
  • + Highest AN Score (8.1) in the storage category — execution quality is industry-leading
  • + Fine-grained IAM policies allow scoped, least-privilege access for agent credentials

Weaknesses

  • − Egress fees are significant — $0.09/GB for data leaving AWS (the hidden cost that compounds)
  • − IAM complexity is real — agents need correctly configured policies, which is a non-trivial setup step
  • − Access readiness (7.2) trails execution quality (8.6) — the API is excellent but onboarding is harder
  • − Multi-region replication adds cost and config complexity vs R2's automatic global distribution

Agent fit

Best for agents already in the AWS ecosystem or needing cross-service integration. The SDK breadth means any agent framework can connect immediately. IAM scoping enables secure BYOK patterns.

Cloudflare R2 7.4/10

The best choice when egress costs matter — which for high-throughput agents, they usually do.

Strengths

  • + Zero egress fees — read as much data as you want without cost anxiety
  • + S3-compatible API — most S3 SDKs work with R2 by changing the endpoint URL
  • + Workers integration enables compute-at-the-edge patterns for data processing
  • + Automatic global distribution without multi-region configuration
  • + Simpler pricing model — no data transfer surprises

Weaknesses

  • − Younger ecosystem — fewer integrations, less battle-tested at extreme scale
  • − No native equivalent of S3 Select, Glacier tiers, or S3 Event Notifications
  • − Confidence score (0.55) reflects less community evidence than S3
  • − Access readiness (7.0) slightly below S3's — fewer auth pattern examples in the wild

Agent fit

Best for agents that read heavily from storage. If your agent retrieves files, serves assets, or processes stored data frequently, R2's zero egress eliminates a cost variable that's hard to predict. S3-compatible API means migration is usually a config change.

Backblaze B2 6.6/10

The budget option for bulk storage. Less polished, but significantly cheaper per GB stored.

Strengths

  • + Lowest storage cost — $0.005/GB/month vs S3's $0.023/GB
  • + S3-compatible API available (alongside native B2 API)
  • + Free egress via Cloudflare Bandwidth Alliance partnership
  • + Simple, transparent pricing with no request-type complexity

Weaknesses

  • − Access readiness score (5.8) is notably lower — fewer SDKs, less documentation, fewer auth examples
  • − Narrower ecosystem — no equivalent of Lambda triggers or Workers integration
  • − Lower confidence (0.52) — less community evidence and fewer runtime-verified reviews
  • − Native B2 API is non-standard — the S3-compatible layer is the practical option for agents
  • − No edge distribution — single-region storage with CDN as an add-on

Agent fit

Best for agents with large cold storage needs and tight budgets. If your agent archives data, stores backups, or holds large media files that are rarely accessed, B2 offers significant savings. Not ideal for latency-sensitive or high-frequency read patterns.

Cost comparison at agent-relevant scale

100GB stored, 500GB read, 50GB written per month

AWS S3

~$49.80

$2.30 storage + $45 egress + $2.50 requests

Cloudflare R2

~$6.25

$1.50 storage + $0 egress + $4.75 operations

Backblaze B2

~$5.50

$0.50 storage + $0 egress* + $5 transactions

*Via Cloudflare Bandwidth Alliance

Quick decision

S3 if you're in the AWS ecosystem, need cross-service triggers, or prioritize SDK breadth and proven reliability at massive scale.
R2 if your agent reads heavily from storage and egress costs would dominate your bill. S3-compatible API makes switching easy.
B2 if you're archiving large volumes of data that's rarely accessed and need the lowest possible storage cost per GB.

Scores are from Rhumb's AN Score — a 20-dimension analysis of execution quality, access readiness, and autonomy readiness, weighted for agent use. Scores update as new evidence is collected. Full methodology →