Mobile App Security: The Checklist Your Users Expect

Users trust your app with their data. A security breach does not just cost money — it costs the trust that took you years to build. Here are eight security fundamentals that every mobile app should implement before launch.

1. Certificate pinning

Your app should only accept TLS certificates that you expect. Without certificate pinning, a compromised network can intercept traffic between your app and your API using a forged certificate. Both iOS and Android provide APIs for this — use them.

2. Encrypted local storage

Never store sensitive data in plain text on the device. Use the platform's secure storage: Keychain on iOS, EncryptedSharedPreferences on Android. This includes auth tokens, user credentials and any personal data that persists between sessions.

3. Token rotation

Access tokens should expire. Refresh tokens should rotate — every time a refresh token is used, the old one is invalidated and a new one is issued. This limits the damage window if a token is compromised and makes stolen tokens self-expiring.

4. Input validation on the server

Client-side validation is a UX convenience. Server-side validation is a security requirement. Never trust input from the app — validate, sanitise and parameterise every value on the server before it touches your database or any downstream service.

5. Biometric authentication

For sensitive actions — payments, profile changes, data exports — require biometric confirmation even if the user is already logged in. This protects against device theft and shoulder surfing. Both platforms provide robust biometric APIs that handle the complexity for you.

6. Obfuscation and tamper detection

Production builds should be obfuscated (ProGuard on Android, bitcode on iOS) and should detect tampering at runtime. If someone decompiles your app and modifies it, the app should refuse to run. This is not security through obscurity — it is defence in depth.

7. Minimal permissions

Request only the permissions your app needs, and request them at the moment they are needed. An app that asks for camera, microphone, location, contacts and calendar on first launch looks suspicious — and users increasingly deny blanket permission requests.

8. Dependency auditing

Your app's security is only as strong as its weakest dependency. Run automated vulnerability scans on every build. Tools like Dependabot, Snyk and Socket flag known vulnerabilities in your dependency tree before they ship to users.

Security is not a feature

Security is not something you add after launch. It is a quality standard that runs through every decision — from how you store data to how you handle errors to how you log events. The checklist above is a starting point, not a finish line. Treat security as an ongoing practice, not a one-time audit.