Skip to main content

Free, Secure, and Open-Source Backup for Microsoft 365

The #1 open-source backup tool for Microsoft 365

Powershell logo

What Corso Users Say

“Documentation is great... initial steps for setup are really useful.”

Microsoft 365 Administrator

"I liked the tool a lot. But once I connected with the team on Discord, I could see that this team really knows what they're doing. That made me a lot more confident."

Kias Hanifa, CTO, Fonicom

"Corso is a fantastic tool, especially the backend logic with Kopia that lets me run incremental backups"

Backup Administrator

Key Features

See why Corso is a perfect fit for your Microsoft 365 backup and recovery needs.

Comprehensive Workflows

High Throughput

Fault Tolerance

End-to-End Encryption



Open Source

Choice of Object Storage

Retention Policies

Why Everyone Loves

Group discussion


The Corso community provides a venue for Microsoft 365 admins to share and learn about the importance of data protection as well as best practices around Microsoft 365 secure configuration and compliance management.

  • Community-led blogs, forums, and discussions
  • Public and feedback-driven development roadmap
  • All community contributions welcome
Approval of fingerprint security

Data Security

Corso provides secure data backup that protects customers against accidental data loss and service provider downtime.

  • End-to-end zero-trust AES-256 and TLS encryption
  • Support for air-gapped backup storage
  • Choice of backup storage provider and geo location
Data extraction dashboard

Robust Backups

Corso, purpose-built for Microsoft 365 protection, provides easy-to-use comprehensive backup and restore workflows that reduces backup time, improve time-to-recovery, reduce admin overhead, and replace unreliable scripts or workarounds.

  • Constantly updated Microsoft 365 Graph Data engine
  • Purpose-built, flexible, fine-grained data protection workflows
  • High-performance backup and recovery data movers
Adding money to a savings jar

Cost Savings

Corso, a 100% open-source tool, provides a free alternative for cost-conscious teams. It further reduces storage costs by supporting flexible retention policies and efficiently compressing and deduplicating data before storing it in low-cost cloud object storage.

  • Free forever OSS with no licensing costs
  • Client-side compression and deduplication
  • Support for S3-compliant storage including AWS Glacier IA

Frequently Asked Questions

Corso is a good fit for basic backup while Alcion is a better fit if you need increased reliability, security, and support.

Corso has both native binaries and container images for Windows, Linux, and macOS.

Corso currently supports OneDrive, Exchange, SharePoint, and Teams.

Corso supports any S3-compliant object storage system including AWS S3 (including Glacier Instant Access), Google Cloud Storage, and Backblaze. Azure Blob support is coming soon.

If you are unable to find an answer in our documentation, please file GitHub issues for bugs or join the Discord community.

Corso's source code is licensed under the OSI-approved Apache v2 open-source license.

You can request new features by creating a new GitHub issue and labeling it as an enhancement.

Laptop image showing Microsoft 365 icons

Start Protecting Your
Microsoft 365 Data!

Corso (Free and Open Source) or
Alcion (Managed Backup as a Service)

Whether you want to self-host or use a managed service, we have you covered!

Try Alcion

Corso Quickstart