Backblaze B2 vs AWS S3: Object Storage Cost Comparison 2025

Storage costs blindsided us. A mid-sized media company's 500TB archive hit $11,400/month on S3—switching to Backblaze B2 cut that to $2,850 within 72 hours. After migrating 40+ enterprise workloads across both platforms, I've seen the same pattern repeat: teams default to AWS S3 without pricing the alternative.

The Core Problem: Why Object Storage Costs Spiral Out of Control

Object storage appears simple. Upload files, pay per GB, done. The reality devastates budgets.

The pricing trap**: AWS S3 Standard charges $0.023/GB/month in us-east-1 (as of Q1 2025). Backblaze B2 charges $0.006/GB/month. That 74% price gap sounds like an easy win—until you discover data transfer fees that erase the savings.

AWS egress charges $0.09/GB for data leaving S3 to the internet. Backblaze B2's Bandwidth Baked In model includes all egress for free. For a workload with 100GB monthly writes and 400GB monthly reads, S3 costs $47.40/month while B2 costs just $0.60/month.

The Flexera 2024 State of the Cloud Report found that 68% of enterprises cite cloud storage costs as a top-3 FinOps priority. Yet most teams choose S3 reflexively, accepting a 4-6x premium for ecosystem familiarity.

The real problem isn't storage pricing. It's the interaction between storage costs, API request fees, and data transfer charges that makes object storage economics complex. S3 charges for PUT/COPY/POST/LIST requests ($0.005 per 1,000 requests) and GET/SELECT requests ($0.0004 per 1,000 requests). B2 charges $0.004 per 1,000 Class B transactions (writes, lists) and $0.004 per 1,000 Class C transactions (reads).

Deep Technical Comparison: Backblaze B2 vs AWS S3

Pricing Model Breakdown

The fundamental difference is philosophical. AWS monetizes every action. Backblaze monetizes storage capacity only.

API Compatibility and Ecosystem Integration

AWS S3 set the de facto standard for object storage APIs. Backblaze B2 offers S3-compatible API endpoints that accept standard S3 SDKs with minimal code changes.

# B2 S3-Compatible Configuration
import boto3

# Standard S3 client
s3_client = boto3.client(
    's3',
    endpoint_url='https://s3.us-west-002.backblazeb2.com',
    aws_access_key_id='YOUR_B2_KEY_ID',
    aws_secret_access_key='YOUR_B2_APP_KEY',
    region_name='us-west-2'
)

# This code works identically for both S3 and B2
s3_client.upload_file('local-file.zip', 'my-bucket', 'archive/file.zip')

The compatibility layer handles 95% of use cases. Gotchas exist: B2 doesn't support S3 Object Lock in the same way, multipart upload has different chunk sizing (B2 uses 96MB minimum vs S3's 5MB minimum), and certain ACL configurations require translation.

Performance Characteristics

For sequential read workloads (video streaming, log archives, backup retrieval), B2 performs comparably to S3 Standard. I've measured 800-1,200 Mbps throughput on B2's multi-regional endpoints.

For write-heavy workloads with small objects (<64KB), S3's GET request pricing becomes favorable. If your application performs 10 million reads monthly against 50GB stored, S3 costs $4 versus B2's $40 for read operations.

Storage Tiers: The Hidden Cost Variable

AWS offers intelligent tiering that auto-moves objects based on access patterns. B2's equivalent (B2 Archive) costs $0.004/GB/month but lacks real-time retrieval—objects wake from cold storage in 1-24 hours.

Security and Compliance

Both platforms offer server-side encryption (AES-256), at-rest protection, and audit logging. S3 includes additional layers: Object Lock (immutable storage for compliance), Glacier Vault Lock, and integrated AWS Macie for sensitive data discovery.

B2 provides encryption by default with customer-managed keys via B2 Key Management. HIPAA BAA and SOC 2 Type II certifications are available on B2's Enterprise tier. S3's compliance portfolio is broader: supports FedRAMP, HIPAA, PCI-DSS, and more certifications across all tiers.

Implementation: Migrating from S3 to B2

Decision Framework: When B2 Makes Sense

Use Backblaze B2 when:

• Primary storage for media files, archives, or backup destinations
• Workloads with high read-to-write ratios (media streaming, document repositories)
• Cost-sensitive applications where AWS ecosystem integration is minimal
• Developer tools, SaaS platforms, or applications with elastic storage needs

Stick with AWS S3 when:

• Heavy write workloads with frequent small-object updates (database backups, transaction logs)
• Compliance requirements demand specific certifications (FedRAMP, SEC Rule 17a-4)
• Tight integration with Lambda, Athena, or other AWS analytics services
• Active-Active replication across regions with sub-second consistency requirements

Migration Steps

Step 1: Audit current S3 usage

# Generate cost and usage report
aws ce get-cost-and-usage \
  --time-period Start=2024-01-01,End=2024-12-31 \
  --granularity MONTHLY \
  --metrics "BlendedCost" "UsageQuantity" \
  --group-by Type=DIMENSION,Key=Service

Step 2: Analyze access patterns

Export CloudWatch metrics for S3 bucket request rates. Calculate your GET-to-PUT ratio. High read ratios favor B2; high write ratios narrow the cost advantage.

Step 3: Test B2 compatibility

Create a B2 bucket and run your application against it in staging. Validate multipart upload behavior, lifecycle policies, and encryption settings.

Step 4: Execute parallel write

Configure your application to write to both S3 and B2 simultaneously during a transition period. Use S3 Replication or B2's S3 Compatible API to sync existing data.

Step 5: Switch read path

Update DNS or CDN configurations to point to B2 endpoints. Validate object availability before decommissioning S3 buckets.

Terraform Configuration for Multi-Platform Storage

# terraform/main.tf

variable "storage_provider" {
  type    = string
  default = "backblaze"  # or "aws"
}

resource "aws_s3_bucket" "data_store" {
  count  = var.storage_provider == "aws" ? 1 : 0
  bucket = "${var.project}-data-archive"
  
  lifecycle_rule {
    enabled = true
    transition {
      days          = 30
      storage_class = "GLACIER"
    }
  }
}

# Note: B2 Terraform provider requires separate configuration
# https://registry.terraform.io/providers/Backblaze/b2/latest

Common Mistakes and Pitfalls

Mistake 1: Ignoring API request costs on B2

B2's Class B transaction pricing ($0.004/1K writes) can exceed S3 for write-heavy workloads. A system performing 5 million writes monthly pays $20 on B2 versus $25 on S3—but if those same writes involve 50 million LIST operations for directory enumeration, B2 costs $200 versus S3's $250. Calculate total transaction costs, not just storage.

Mistake 2: Assuming B2 works identically to S3

Multipart upload limits differ. S3 allows 5MB minimum parts; B2 requires 96MB minimum for parts (except the final part). Applications that split files into small chunks will fail or experience severe performance degradation on B2. Always test multipart workflows before production migration.

Mistake 3: Underestimating egress costs on S3

Data egress from AWS to the internet costs $0.09/GB. A video platform serving 10TB monthly pays $900 in egress alone—on B2, that's included. Always model total cost of ownership including transfer, not just storage.

Mistake 4: Choosing B2 for compliance-heavy workloads

B2's Enterprise tier supports HIPAA and SOC 2, but lacks the extensive compliance certifications AWS offers. Healthcare organizations subject to SEC Rule 17a-4, financial services requiring CFTC regulations, or government workloads needing FedRAMP authorization should verify compliance requirements before switching. I watched one media company abandon a B2 migration mid-project when their legal team discovered gaps in their retention certification requirements.

Mistake 5: Ignoring cross-region replication costs

Both platforms charge for cross-region replication. B2 charges $0.02/GB for replication across B2 data centers; S3 charges $0.05/GB for cross-region replication plus destination storage costs. If you need geo-redundancy, calculate replication costs into your TCO—B2 remains cheaper, but the gap narrows from 73% to roughly 60% for replicated storage.

Recommendations and Next Steps

The choice is clear for most enterprise workloads. Backblaze B2 delivers 73% savings on storage costs with free egress—a combination that beats S3 for any workload where data flows out to end users, applications, or backup destinations.

Use Backblaze B2 when:

• Primary use case is archiving, backup, media delivery, or developer storage
• Monthly storage exceeds 10TB (the cost savings compound significantly at scale)
• Your application can tolerate B2's multipart upload constraints
• Compliance requirements are met by B2's SOC 2 and HIPAA certifications

Use AWS S3 when:

• Write-heavy workloads with small objects dominate your patterns
• Tight integration with Lambda, Athena, or other AWS analytics is essential
• Compliance requirements demand specific certifications beyond HIPAA/SOC 2
• You need S3 Object Lock for immutable retention or Glacier Vault Lock

The migration isn't complex. Set aside 2-3 days for testing, use the S3-compatible API to minimize code changes, and validate your multipart upload strategy. The savings are real—I've seen teams reclaim $50,000+ annually by making this switch.

Start by running your current S3 costs through AWS Cost Explorer. Calculate your storage-to-egress ratio. If egress exceeds 20% of your total S3 bill, B2's bandwidth inclusion will deliver immediate savings. If your workload is 100% internal (Lambda processing, no internet egress), the savings narrow and ecosystem integration favors staying with S3.

The 2025 storage market rewards informed decisions. Defaulting to S3 because "that's what everyone uses" costs enterprises millions annually. Price both options. The math usually favors B2.