The most useful mobile app security best practices for a solo developer, in priority order, are server-side authorization, no hardcoded secrets, platform secure storage and HTTPS with validated certificates. Obfuscation and root detection come last because attackers can bypass them.
These practices belong inside the wider job of how to how to build a mobile app, so treat them as build-time decisions rather than a final audit. Each item below names the attack it addresses, the effort it asks of one person and where its protection runs out.
How the order was chosen
This is an ordered selection, not an official ranking. The order is editorial judgement built on OWASP’s advice to assume all client-side controls can be bypassed and to repeat them on the server. Controls that hold up even when the attacker controls the device rank above controls that run on the device.
- Attack prevented: the specific failure the control stops, such as stolen credentials, intercepted traffic or an unauthorized API call.
- Solo-developer effort: a judgement of how much work the control adds if you build and maintain the app alone.
- Strength of protection: whether the control holds against a determined attacker or only slows a casual one.
Server-side trust and secrets
Enforce authentication and authorization on the server
Server-side authorization stops attackers who tamper with the app or call your API directly. OWASP says to perform authentication and authorization server-side and to load data onto the device only after authentication succeeds. The same cheat sheet cites M1: Insecure Authentication/Authorization from the OWASP Mobile Top 10, which shows how central this category is.
The effort is low to moderate if you already run a backend. It suits every app that has accounts or private data. The limit is that it protects your data, not the code inside the app.
Keep secrets out of the app
Hardcoded credentials let anyone who downloads your app recover them. OWASP’s instruction is blunt: do not hardcode credentials in the mobile app. A secondary analysis of OWASP guidance adds that hard-coded secrets can be extracted even when the application code appears clean, so tidy code is no defence.
The practical fix is to keep the secret on your server and let the app call your backend. Effort is low, and it is one of the highest-value changes you can make.
Secure storage on the device
Tokens and keys that must live on the device belong in the platform’s secure store. OWASP recommends platform-specific secure storage such as Keychain (iOS) or Keystore (Android). That answers the question of where to keep session tokens: in the Keychain on iOS and the Android Keystore on Android, rather than in files you manage yourself.
Where the hardware allows it, go a step further. OWASP advises leveraging hardware-based security features when available, such as Secure Enclave on iOS and Strongbox on Android. Effort is low to moderate because you call platform APIs instead of writing cryptography. It suits any app that holds long-lived tokens, and it adds the most protection when a device is lost or its files are copied.
Securing API communication
HTTPS and certificate validation
Encrypted, validated connections stop attackers on the network from reading or altering traffic. OWASP’s baseline is to use HTTPS for all network communication, with strong, industry-standard cipher suites, appropriate key lengths and certificates signed by a trusted CA provider. It also says not to override SSL certificate validation to allow self-signed or invalid certificates.
That last rule trips up many developers. A shortcut that disables validation to get a staging server working can silently ship to production. Fix the staging certificate instead. Effort is low, and the control is essential for every app that talks to a server.
Token-based authentication
Tokens limit the damage of a stolen session. OWASP recommends OAuth2, JWT or similar for secure authentication, with keys and tokens rotated regularly. Your server still has to check every request, because the token proves identity only when the backend validates it.
Certificate pinning
Certificate pinning narrows which certificates your app will accept for your API. OWASP’s wording is to consider certificate pinning and to read the Pinning Cheat Sheet for its pros and cons, so it is a decision rather than a default. For a solo developer, get HTTPS and validation right first. Add pinning when the data justifies the extra care it needs.
Measures that give limited protection
Code obfuscation
Obfuscation makes the release binary harder to read, but it does not make secrets safe. OWASP lists obfuscating the app binary among its integrity controls. On Android, ProGuard and R8 are the tools usually used for this in release builds.
Because OWASP also says to assume client-side controls can be bypassed, treat obfuscation as a speed bump. Turn it on if your build tool makes it cheap, and never let it replace moving secrets and authorization to the server. That is the clearest answer to whether code obfuscation actually protects your app: it adds friction, not protection.
Root and jailbreak detection
Detection is worth adding only as one signal among several. OWASP lists a check to detect if the app is running in an emulator or on a rooted or jailbroken device, alongside checks for signs of debugging, hooking or code injection. It also leaves the response to you, for example limiting functionality, rather than demanding a hard block.
So should you detect jailbroken or rooted devices? Yes for apps handling payments or sensitive data, where reducing functionality on a modified device is a reasonable risk decision. For low-risk apps, the effort is rarely worth it. Since the check runs on the device, an attacker who controls the device can bypass it, so keep the real decisions on the server.
On Android, the Play Integrity API helps check that interactions and server requests come from your genuine app binary running on a genuine device. It moves part of the check toward your server, which makes it a stronger signal than a purely local test. If you show a warning or limited mode, make it clear and usable for everyone, following the same standards as mobile app accessibility.
Priority comparison
| Practice | Attack it prevents | Solo-developer effort | Planning use |
|---|---|---|---|
| Server-side authentication and authorization | Tampered or bypassed client-side checks | Low to moderate | Do first; it holds even if the app is modified |
| No hardcoded secrets | Credentials extracted from the app package | Low | Move secrets to the backend before release |
| Keychain or Android Keystore storage | Tokens read from device storage | Low to moderate | Use for every stored token or key |
| HTTPS with validated certificates | Traffic interception and alteration | Low | Never override validation, even for testing |
| Certificate pinning | Interception through an untrusted certificate | Moderate | Add after reviewing pros and cons |
| Code obfuscation | Easy reading of the binary; delays rather than blocks | Low | Optional extra with limited protection |
| Root and jailbreak detection | Running on a modified device; bypassable | Moderate | Use as a risk signal for sensitive apps only |
The practices and their limits come from the OWASP Mobile Application Security Cheat Sheet and analysis of OWASP’s mobile guidance, while the effort ratings are editorial judgement for a solo developer.
Using the OWASP checklist
The OWASP Mobile Application Security Verification Standard (MASVS) is the closest thing to a mobile app security checklist. One analysis recommends using it as the control baseline for mobile authentication, storage, communication and resilience requirements. Its control groups highlight the most critical areas of the mobile attack surface, and they line up with the sections of this list.
MASVS says what to verify. The companion testing guide, MASTG, describes the processes, techniques and tools used during a mobile app security test. The OWASP Mobile Top 10 plays a different role. It should be treated as a prioritisation aid, followed by a verification standard such as MASVS and MASTG. Use the Top 10 to decide what to fix first, then work through MASVS before release. Once the app passes, the next job is getting it found, which app store optimization covers.
Frequently asked questions
What are the most important security practices for a mobile app?
Start with OWASP’s design principles of least privilege, defense in depth and separation of concerns. Android’s guidance adds that you should minimize the number of permissions your app requests. Then apply the ordered list above, beginning with server-side authorization.
Can I write my own encryption for stored data?
No. OWASP says do not attempt to implement your own encryption algorithms. Use the platform APIs and secure stores instead.
Is Android external storage safe for tokens or sensitive files?
No. Files on external storage are globally readable and writable, so Android advises storing only non-sensitive information there. Files created on internal storage are accessible only to your app by default.
Does the platform protect my app without extra work?
Partly. Android states that its built-in security features significantly reduce the frequency and impact of application security issues. They do not cover choices that are yours alone, such as hardcoded secrets or disabled certificate validation.
