Android System Key Verifier is a security component that checks the integrity and authenticity of the operating system on Android devices. It verifies whether the system partitions (boot, system, recovery, etc.) are digitally signed by the manufacturer, helping to protect both users and app developers.

Android System Key Verifier does not directly display pop-up warnings, but it indirectly informs the user that the system has been “modified” through the following ways:

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1. 📱 Warnings on Device Startup
   On devices with an unlocked bootloader, a screen like the one below appears during boot:
   ⚠️ “Your device software can’t be checked for corruption. Please lock the bootloader.”
   This screen usually stays for 5–10 seconds and warns the user about root/ROM modifications.

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2. 🧪 SafetyNet / Play Integrity Tests Fail
   Banking, gaming, and security-focused apps (such as Google Wallet, Netflix, Pokemon GO) test for system integrity.
   If the System Key Verifier fails:

• These apps may not work or may open in limited mode.

• A warning like “Your device is not secure” may appear.

3. 🛍️ Google Play Protect Certification Disabled
   Go to: Settings > Google > Play Protect > Is the device certified?
   If it says “Not certified”, system verification has failed.

4. 📥 OTA Updates Are Blocked
   If the manufacturer’s OTA (Over-the-Air) updates detect the system as “modified”, the updates won’t be installed