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Restore OEM Unlock Toggle on Galaxy S23 (SM-S911B) by Downgrading One UI 8 → One UI 7

After Samsung's One UI 8 update (Android 16) removed the OEM Unlock toggle, I decided to test a safe downgrade. It worked! I got the OEM Unlock option back and successfully unlocked the bootloader. Here's the full breakdown for anyone stuck in the same situation.

⚠️I'm NOT responsible for any damage or bricks that could happen to your phone.

Device Info

  • Model: Galaxy S23 SM-S911B
  • Original Build: S911BXXU8EYI5 (One UI 8 / Android 16)
  • Downgraded Build: S911BXXS8DYI3 (One UI 7 / Android 15)
  • Binary / SW Rev: U8 (same for both this is critical !!!)

Files & Tools

Firmware sources:

Odin Version:

  • Use Odin v3.14.4 or newer. (The newer modded Odin3 v3.14.4_3B_Patched also works fine.)
  • Odin Download

What to download:

  • Full firmware package for your exact CSC (region) → contains BL, AP, CP, CSC, USERDATA

Odin Instructions

Before flashing:

  1. Extract firmware .zip → get the .tar.md5 files.
  2. Load them in Odin as follows:
Slot File
BLBL_…tar.md5
APAP_…tar.md5
CPCP_…tar.md5
CSCCSC_…tar.md5 (not HOME_CSC)
USERDATAUSERDATA_…tar.md5

Odin Options: ✅ Auto-Reboot    ✅ F.Reset Time    ❌ Re-Partition (leave unchecked)

Then:

  1. Boot phone to Download Mode (Vol Up + Vol Down + USB-C).
  2. Click Start in Odin.
  3. Wait — don’t touch cables.
  4. Wait until Odin shows PASS (can take 8–10 min).
  5. Let phone reboot automatically.
  6. On setup, connect to Wi-Fi immediately.
  7. Leave on “Checking info” screen — mine took ~20 min.
  8. When setup finishes → Settings → About phone → Software info → tap Build Number ×7 → Developer Options.
  9. OEM Unlock toggle appeared!
  10. Enable it → confirm → phone factory-resets → bootloader unlocked ✅

Notes

  • Patience is everything. The “Checking info” stage lets KG/VaultKeeper sync with Samsung.
  • Stay on Wi-Fi and don’t interrupt.
  • If it hangs too long (~30 min), one gentle reboot is safe.
  • Do not flash One UI 8 afterward — it hides OEM Unlock again.
  • Make sure the firmware binary level (U8) matches or Odin will refuse to flash.

Result

Downgrading from One UI 8 → One UI 7 on the same binary revision (U8) restored my OEM Unlock toggle on Galaxy S23 (SM-S911B). After enabling it, the bootloader unlocked normally.

Hopefully this helps anyone stuck without OEM Unlock after updating!