How to Secure Your Fly.io App
Last updated: April 20, 2026
Fly.io enables global edge deployment. This guide covers securing applications deployed across Fly.io's global network.
Why Security Matters for Fly.io
Key Security Concerns
- Multi-region secrets sync can fail silently - verify with 'fly secrets list'
- Persistent Volumes are not encrypted by default - encrypt at app level
- fly.toml config is in repo - don't put secrets in config file
- Network complexity: 6PN, Private Networking, Flycast - easy to misconfigure
- Root access means you own security patching (unlike managed serverless)
Security Strengths
- Firecracker microVMs provide hardware-level isolation (same as AWS Lambda)
- Private Networking: internal WireGuard mesh across all your machines globally
- 'fly secrets' encrypts and syncs credentials across all regions automatically
- Global edge means DDoS traffic is absorbed at 30+ points of presence
- Full container control - run your own security tools inside the VM
Step-by-Step Security Guide
1. Manage Secrets Properly
Use 'fly secrets set' to store secrets. They're encrypted and synced across regions automatically.
fly secrets set DATABASE_URL=postgres://...2. Configure Private Networking
Use Fly's private network for service-to-service communication. Don't expose internal services publicly.
3. Secure Volume Data
Data on Fly volumes persists. Encrypt sensitive data at the application level if needed.
4. Set Up Health Checks
Configure health checks to detect compromised instances. Unhealthy instances are replaced automatically.
5. Use Fly Proxy for TLS
Fly's proxy handles TLS termination. Ensure your app properly reads X-Forwarded-* headers.
6. Monitor with Fly Metrics
Use Fly's built-in metrics to detect unusual traffic patterns that might indicate attacks.
Common Security Mistakes
Avoid these common Fly.io security pitfalls:
- Secrets in Dockerfile or fly.toml
- Internal services exposed publicly
- Unencrypted sensitive data on volumes
- Missing health checks
- Ignoring X-Forwarded headers
Recommended Security Tools
Use these tools to maintain security throughout development:
Ready to Secure Your App?
Security is an ongoing process, not a one-time checklist. After implementing these steps, use vas to verify your Fly.io app is secure before launch, and consider regular scans as you add new features.
Frequently Asked Questions
Are Fly secrets secure across regions?
Yes, Fly encrypts secrets and syncs them to all regions running your app. They're decrypted only when your app starts.
How do I secure internal services on Fly?
Use Fly's private networking with .internal domains. Internal services communicate over encrypted WireGuard tunnels without public exposure.
Explore Related Resources
More on Fly.io Security
Every angle of Fly.io security, from the specific findings we detect to step-by-step fixes.
Fly.io Security Risks
Specific risks we find in Fly.io apps, with real-world examples.
Fly.io Security Issues
Issues grouped by severity with detection and fix steps.
Fly.io Best Practices
Remediation playbook derived from Fly.io's actual failure modes.
Is Fly.io Safe?
Honest assessment of Fly.io's production readiness.
Can Fly.io Apps Be Hacked?
Attack vectors specific to Fly.io and how they get exploited.