Backblaze B2 Cloud Storage API
Backblaze B2 is an S3-compatible object storage service at 1/4 the price of AWS S3 — store files, generate download URLs, and serve content via CDN with 10 GB free storage and $0.006/GB egress.
Score Breakdown
⚙ Agent Friendliness
🔒 Security
Restricted application keys for bucket-scoped access. Server-side encryption available. No IAM or fine-grained attribute-level control like S3. GDPR compliant with EU region option. HTTPS enforced.
⚡ Reliability
Best When
You need cheap, reliable object storage with S3 compatibility and don't require AWS-specific integrations — especially for static assets served via Cloudflare.
Avoid When
You need AWS S3's full ecosystem (Lambda triggers, SQS, IAM per-prefix access, Storage Lens) or strict compliance certifications.
Use Cases
- • Budget-friendly file storage for agent-generated content (images, documents, exports)
- • Backup storage for agent-produced artifacts that don't need AWS S3's full feature set
- • Serving static assets via Cloudflare CDN integration (Backblaze + Cloudflare = free egress)
- • Long-term archival of agent output with lower cost than Glacier alternatives
- • S3-compatible drop-in replacement for teams wanting to reduce storage costs
Not For
- • Applications requiring AWS-specific features (SQS triggers, Lambda events, IAM fine-grained control)
- • Teams with strict compliance requirements (B2 has fewer compliance certifications than S3)
- • High-frequency small object operations (S3 API overhead is real for millions of tiny files)
Interface
Authentication
Application Key (accountId + applicationKey). Master Application Key has full access; restricted Application Keys can be scoped to specific buckets, name prefixes, and operations. Use restricted keys for agents.
Pricing
Significantly cheaper than S3. Pairing with Cloudflare eliminates egress costs entirely. No minimum spend.
Agent Metadata
Known Gotchas
- ⚠ Authorization tokens from b2_authorize_account expire in 24 hours — agents must implement token refresh
- ⚠ Large file uploads (>100MB) require 3-step process: startLargeFile → uploadPart (per 5MB+ chunk) → finishLargeFile
- ⚠ B2 native API and S3-compatible API have different endpoint URLs and auth — don't mix them in same codebase
- ⚠ File versioning is disabled by default — overwriting a file permanently deletes the old version unless versioning enabled
- ⚠ Download URL for private files requires generating signed URLs with b2_get_download_authorization — not intuitive first time
Alternatives
Full Evaluation Report
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Scores are editorial opinions as of 2026-03-07.