Secure your Fly.io application with these essential practices. From authentication to deployment security.
Verify your app follows these best practices automatically.
Building with Fly.io requires attention to security. These best practices help you ship secure applications while maintaining development velocity.
Never hardcode API keys, database credentials, or secrets in your code.
Store secrets in environment variables, add .env to .gitignore
Use established authentication libraries rather than custom implementations.
Use auth libraries like Auth0, Clerk, NextAuth, or platform-native auth
Ensure users can only access resources they're authorized to view or modify.
Check user permissions server-side for every protected operation
Never trust data from users. Validate type, length, and format on the server.
Use validation libraries like Zod or Yup for input validation
Encrypt all traffic and add security headers to prevent common attacks.
Enforce HTTPS, add CSP, HSTS, X-Frame-Options headers
Regularly update packages to patch known vulnerabilities.
Run npm audit regularly, use Dependabot or similar
Secrets get committed to git and exposed
Always use environment variables for credentials
Client-side checks can be bypassed
Always validate on the server
Users can access other users' data
Check permissions on every protected operation
Following best practices is the first step. Verify your app is actually secure with a comprehensive security scan.
Scan Your App FreeAt minimum: secrets in environment variables, proper authentication, authorization checks on all endpoints, and HTTPS. These basics prevent the most common attacks.
Yes. A quick security scan can catch common issues like exposed secrets, missing headers, and misconfigurations that are easy to miss during development.
Fly.io provides security features, but they require proper configuration. Follow security best practices and run a security scan before deploying to production.
Last updated: January 2026