How to Build Secure Mobile Apps: Mobile App Security Best Practices

Building a secure mobile app means assuming the device and network can't be fully trusted. Keep secrets and business rules on the server, authenticate users properly and authorize every API request, encrypt traffic and use platform secure storage for sensitive data, keep dependencies updated, avoid logging sensitive information, and test against OWASP's Mobile Application Security Verification Standard (MASVS). Add resilience measures such as obfuscation, app attestation and compromised-device checks in proportion to the app's risk.

A mobile app runs on hardware you don't control. Attackers can install it on a rooted or jailbroken device, inspect its code, intercept its traffic on networks they control, and call your API directly without the app at all. Security therefore has to live mainly on the server, with the app designed so that a compromised copy can't do more damage than a legitimate user could.

List what the app protects (accounts, payments, health data, business data), who might attack it, and how: stolen devices, malicious networks, reverse engineering, abused APIs, compromised SDKs. Rank risks by impact and likelihood, then choose controls. A banking app and a recipe app need very different depth.

OWASP's Mobile Application Security project provides the MASVS standard and a testing guide. MASVS groups requirements into control areas that make a useful checklist structure.

Use proven sign-in methods, short-lived tokens and secure token storage, covered in depth in mobile app authentication. Then enforce authorization on the server for every request. Broken object-level authorization, where changing an ID in a request returns someone else's data, remains one of the most common API flaws.

Treat the API as public, because it effectively is. Authenticate and authorize every endpoint, validate all input, return only the fields the app needs, rate-limit sensitive operations, and log security-relevant events. The secure development guide covers the server side in more detail.

Use HTTPS everywhere with modern TLS. iOS App Transport Security and Android's network security configuration both block cleartext traffic by default; don't add exceptions without a strong reason. Never disable certificate validation, even in debug code that might ship. Certificate pinning adds protection for high-risk apps but needs a rotation plan so a certificate change doesn't lock users out.

Store the minimum sensitive data on the device. Keep credentials and keys in the iOS Keychain and Android Keystore. Use iOS data protection classes and Android encrypted storage for sensitive files and databases. Exclude sensitive data from backups where appropriate, and clear it on logout.

Anything in the app binary can be extracted, so there's no safe place to hide a secret key in a mobile app. Keep secret keys on your backend, proxy third-party calls that need them, and give the app only short-lived, narrowly scoped credentials. Public identifiers meant for client use, such as some SDK keys, should still be restricted to your app where the provider allows it.

Expire sessions appropriately, revoke tokens on logout and password change, and bind sensitive actions to recent authentication. Validate input on the server even if the app validates it too, and treat deep link parameters, push payloads and data from other apps as untrusted input. See mobile app deep linking for link-specific risks.

Third-party SDKs run with your app's permissions and see your users' data. Vet SDKs before adding them, keep them updated, scan dependencies for known vulnerabilities, and remove unused ones. Inadequate supply chain security is a named risk in the OWASP Mobile Top 10.

Obfuscation (such as R8 on Android) makes reverse engineering slower. Root and jailbreak detection can flag risky environments but is routinely bypassed. App attestation services, Play Integrity on Android and App Attest on iOS, let your server check that requests come from a genuine app on a genuine device. Use these in layers, proportionate to risk, and keep critical decisions on the server.

Never log passwords, tokens, full card numbers, health details or personal identifiers. Check that crash reports and analytics events don't capture them either; see crash reporting and monitoring. Strip verbose debug logging from release builds.

Keep business rules, pricing, entitlements and fraud checks on the server. Separate environments, restrict admin access, encrypt sensitive data at rest, and monitor for anomalies. See mobile app backend development for the components involved.

Scan code and dependencies automatically on every build, review against MASVS, use the OWASP Mobile Application Security Testing Guide for manual checks, and commission penetration testing for higher-risk apps and major releases. Include security cases in regular QA, as described in mobile app testing.

Secure mobile apps assume the device, network and binary can be inspected, and keep the decisions that matter on the server. Use OWASP MASVS as a structure, protect storage, network and credentials, manage dependencies, and test regularly. For what data you should collect in the first place, see mobile app data privacy. For the wider build context, see the mobile app development guide.