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### Locking DNS Settings on Android Without Root Using ADB

Based on current discussions from Android forums, Reddit, and XDA (as of September 2025), there's no standalone "app" that directly locks the Private DNS setting (Android's system-level DNS override) without root. However, you can achieve this using **ADB (Android Debug Bridge)** commands to disable the specific Private DNS activity in the Settings app, making it inaccessible via the UI. This prevents easy changes to your DNS (e.g., to adult-filter-dns.cleanbrowsing.org for ad-blocking or content filtering) while keeping the rest of Settings functional.

This method is free, non-root, and persistent across reboots—ideal for parental controls or self-accountability. It works on Android 9+ (tested up to Android 15 on Pixels and Samsungs). Drawbacks: Users can still change DNS via ADB (if they enable USB debugging) or third-party apps, and it might break on major OS updates. For more enforcement, combine with an app locker like Norton App Lock (free tier) to password-protect the full Settings app.

#### Why ADB for Locking?

- Android's Private DNS is a secure global setting, but its UI entry point (com.android.settings/.network.PrivateDnsSettingsActivity) can be disabled via ADB's package manager.

- No app does this natively without ADB or root because it requires `WRITE_SECURE_SETTINGS` or component disabling permissions.

- Alternatives like RethinkDNS or MacroDroid can *set* DNS dynamically but need a one-time ADB grant for automation—not true "locking."

#### Step-by-Step Guide to Lock Private DNS Activity

1. **Enable Developer Options & USB Debugging**:

- Go to Settings > About Phone > Tap "Build Number" 7 times.

- Back to Settings > System > Developer Options > Enable "USB Debugging."

2. **Set Up ADB on Your Computer**:

- Download platform-tools from Google's developer site (developer.android.com/too[...]s/releases/platform-tools).

- Extract to a folder (e.g., C:\platform-tools on Windows).

- Connect your phone via USB, unlock it, and allow the debugging prompt.

3. **Set Your Desired Private DNS (If Not Already Done)**:

- Open a command prompt/terminal in the platform-tools folder.

- Run: `adb devices` (authorize if prompted).

- Set DNS (replace with your choice, e.g., adult-filter-dns.cleanbrowsing.org for adult filtering):

```

adb shell settings put global private_dns_mode hostname

adb shell settings put global private_dns_specifier adult-filter-dns.cleanbrowsing.org

```

- Verify: `adb shell settings get global private_dns_specifier` (should output your DNS).

4. **Lock the Private DNS Settings Activity**:

- Run:

```

adb shell pm disable-user com.android.settings/.network.PrivateDnsSettingsActivity

```

- If it says "Success," reboot your phone: `adb reboot`.

- Test: Go to Settings > Network & Internet > Private DNS—it should be missing or grayed out.

5. **Unlock If Needed** (Reversible):

- Run: `adb shell pm enable com.android.settings/.network.PrivateDnsSettingsActivity`

- Reboot.

#### Comparison of Related Apps & Methods

If pure locking isn't enough, these apps use ADB for enhanced DNS control (grant once via `adb shell pm grant [package] android.permission.WRITE_SECURE_SETTINGS`). They're free and non-root but focus more on management than hard locks.

| App/Method | Key Feature | ADB Required? | Locking Strength | Best For | Drawbacks |

|------------|-------------|---------------|------------------|----------|-----------|

| **ADB Disable Activity** (Direct Command) | Hides Private DNS UI entirely | Yes (one-time) | High (UI inaccessible) | Permanent lock without apps | Reversible only via ADB; may fail on some OEMs (e.g., Xiaomi) |

| **MacroDroid** (Automation App) | Auto-toggles DNS on WiFi/mobile; lock via profiles | Yes (for secure settings) | Medium (app-locked automation) | Dynamic switching (e.g., disable on work WiFi) | Learning curve for macros |

| **RethinkDNS** | Sets/encrypts DNS (DoH/DoT); app PIN lock | No (but ADB for advanced) | Medium (app-level PIN; firewall extras) | Ad-blocking + analytics | Persistent notification; VPN-based |

| **PrivateDNS QuickToggle** | Quick tile to toggle DNS on/off | Yes (grant permission) | Low (easy toggle, but lockable via app locker) | Quick access without full lock | Not a lock—more a convenience tool |

| **Norton App Lock** (Fallback) | Password-locks entire Settings app | No | Medium (broad protection) | Simple UI lock if ADB fails | Locks more than just DNS; free with ads |

#### Tips & Troubleshooting

- **Compatibility**: Works on stock Android/Pixel; on Samsung/Xiaomi, you might need `adb shell pm disable-user --user 0` variant. If it fails ("component not found"), search your ROM's activity name via `adb shell dumpsys package com.android.settings | grep DNS`.

- **Bypass Prevention**: Disable USB Debugging after setup (re-enable only when needed). Use Family Link (Google's free parental app) for remote monitoring.

- **Alternatives Without ADB**: For non-locking DNS changes, use built-in Private DNS or apps like DNS Changer (VPN-based, no lock). For kids, Qustodio's free tier adds DNS filtering but requires a subscription for locks.

- **Security Note**: Always use reputable DNS like AdGuard (dns.adguard.com) or NextDNS for blocking adult content/ads.

This ADB method is the most direct "lock" per 2025 XDA/Reddit consensus. If your device/ROM differs (e.g., Android TV), share details for tweaks!