Last Updated: June 3, 2026
Restoring your SM-G998U is a straightforward process when you use the official Samsung Galaxy S21 Ultra 5G SM-G998U firmware. This page provides every file and instruction you need for FRP bypass, hard resets, IMEI repair, and complete flashing.
Device: Samsung Galaxy S21 Ultra 5G SM-G998U | Chipset: Qualcomm SM8350 Snapdragon 888 5G | Flash Tool: Odin
Android: Android 11, One UI 3.1 | File Type: .tar.md5 / ZIP (Contains AP, BL, CP, CSC files for Odin)
⚠ Warning: Flashing erases all data. Back up first.
Samsung Galaxy S21 Ultra 5G SM-G998U Firmware (Flash File) Drivers, Tools & Guide
Installing the official software on your Samsung Galaxy S21 Ultra 5G SM-G998U requires the correct Odin version and the right firmware files. Everything you need is organized on this page, including the specific Samsung Galaxy S21 Ultra 5G SM-G998U firmware, the required tools, and step-by-step instructions.
Before you begin, check if your phone has a Samsung account actively signed in. You must sign out of this account before doing anything else. Skipping this step will trigger Knox security, and dealing with a KG lock after a flash takes much more effort to fix. Samsung firmware packages arrive in a .tar.md5 format. Once you extract the main ZIP folder, look for files labeled AP_*, BL_*, CP_*, and CSC_* (or HOME_CSC_*). If these specific files are missing, you have downloaded the incorrect package.
Your Samsung Galaxy S21 Ultra 5G SM-G998U firmware download arrives as a compressed ZIP archive. You will need to extract it using WinRAR or 7-Zip. Once extracted, verify that you see files such as AP_*.tar.md5, BL_*.tar.md5, CP_*.tar.md5, and CSC_*.tar.md5 (or HOME_CSC_*.tar.md5). If these files are not present, the firmware package does not match your device.
Keep in mind that installing stock firmware will completely wipe your phone. This is intentional, as it clears out deep software issues like FRP locks, system crashes, sluggish performance, forgotten screen locks, a device stuck on the logo, connectivity bugs, rapid battery drain, and soft brick conditions.
Hard Reset Samsung Galaxy S21 Ultra 5G SM-G998U
You can perform a factory reset on the Samsung Galaxy S21 Ultra 5G SM-G998U without a computer by using the hardware button combination. Turn the phone off entirely, then press and hold Volume Up + Power (if you have an older model with a physical Home button, press Volume Up + Home + Power) until the recovery menu loads. Use the volume keys to highlight “Wipe Data/Factory Reset” and press the Power button to confirm.
A hard reset completely clears your data and returns the Samsung Galaxy S21 Ultra 5G SM-G998U to its factory state. This process resolves the majority of software glitches, including app crashes, lagging, bootloops, and forgotten passwords. If the phone still experiences problems after a factory reset, you will need to perform a full firmware installation using Odin, which is detailed in the sections below.
Samsung Galaxy S21 Ultra 5G SM-G998U FRP Bypass
The most effective way to bypass FRP on the Samsung Galaxy S21 Ultra 5G SM-G998U is by using a free Android apps launcher during the initial setup. Following a factory reset or a firmware flash, you might encounter a Google account lock (FRP). You can use our free Android apps launcher to quickly get past this screen. This is exactly why you should always remove your Google account before flashing, it prevents the lock from triggering in the first place.
Why Do We Need Samsung Galaxy S21 Ultra 5G SM-G998U Firmware?
Flashing the official Samsung Galaxy S21 Ultra 5G SM-G998U firmware is necessary to resolve deep software issues like bootloops, system freezes, or update failures. Samsung devices are flashed using Odin, regardless of the internal processor. Installing the official software can fix the following problems:
- Unlock a phone that has been disabled or locked.
- Upgrade the operating system to the most recent Android version supported by the hardware.
- Clear up freezing, lagging, and continuous startup loops on your SM-G998U.
- Fix battery draining rapidly or over-the-air update failures.
- Return the device to the original stock ROM to maintain warranty status.
- Repair a phone that will only boot into the recovery mode screen.
- Recover from Knox or KG lock issues caused by an interrupted or incorrect flash.
Learn more about stock ROMs and why flashing works.
Choosing the Right Firmware Version
Selecting the correct firmware version for your Samsung Galaxy S21 Ultra 5G SM-G998U requires matching the exact model number, region code, and binary level. Installing an incompatible file can cause severe damage to the software:
- Identify Your Exact Model Number: Open Settings › About Phone and write down the complete model number (for example, SM-G998U). The letter at the end is crucial, U/U1 means USA, W means Canada, N means Korea, and B/F means International/Global. Installing a file meant for a different variant will cause system errors.
- Match the CSC (Region): The 3-letter region code in the firmware name must align with your phone. Check Settings › About Phone › Software Information for your active CSC, or look at the Service Provider line in Download Mode. Common codes include XAA (US), BTU (UK), INS (India), and SER (Russia).
- Check the Binary Level: Look at the version string in your current software (for instance,
XXU9BZDP, the number immediately following the letters is the binary level). You cannot downgrade past this number. If your phone operates on Binary 9, you must use Binary 9 or higher. - Confirm the Build Date: The final 4 characters of the PDA version indicate the build date. The first character represents the year (A=2024, B=2025, C=2026), and the second represents the month (A=January through L=December).
- Verify in Download Mode: Turn the phone off, then hold Volume Down + Power to access Download Mode. This screen lists your exact model, CSC, and software version, use this information to confirm your choice before proceeding.
Firmware Details for Samsung Galaxy S21 Ultra 5G SM-G998U
Here is a quick overview of the official firmware specifications:
| Firmware Information | Details |
|---|---|
| Device Model | Samsung Galaxy S21 Ultra 5G SM-G998U |
| Firmware Version | N/A |
| File Size | N/A |
| Android Version | Android 11, One UI 3.1 |
| Platform | Qualcomm SM8350 Snapdragon 888 5G |
| Release Date | Released 2021, January 29 |
| Region | Global, Africa and Asia |
| File Type | .tar.md5 / ZIP (Contains AP, BL, CP, CSC files for Odin) |
Which Firmware Version Should I Download?
This is a common question, so I have created a simple reference table. Locate your specific scenario below to find the correct file:
| Your Situation | What I Recommend |
|---|---|
| Phone is completely dead or stuck on logo | the latest version, download this one. It is the latest Samsung Galaxy S21 Ultra 5G SM-G998U firmware available. |
| FRP / Google account lock only | See the FRP bypass guide above, you likely do not need the full firmware for this. |
| Not sure which region/CSC to download | Check Settings › About Phone › Software Information for your current CSC, or enter Download Mode (Volume Down + Power), it shows the CSC on screen. Match the 3-letter code (e.g. XAA, BTU, INS) to the firmware filename. |
| Phone slow after a recent OTA update | Try the next older version, sometimes the latest OTA introduces new bugs and an older build runs better. Make sure the binary level is the same or higher than what your device currently has. |
| IMEI missing after a previous flash | Re-flash the latest version first, then follow the IMEI repair guide. Do not skip the reflash. |
| the latest version failed with a flash error | Try the next older version instead and double-check your AP/BL/CP/CSC file assignments in Odin before assuming the firmware is the problem. |
| Restoring to factory / warranty repair | the latest version, clean state, fresh start. |
To tell which Samsung firmware is newer, look at the last 4 characters of the PDA version string (e.g. S938BXXU9CZDP). The first character is the year (A=2024, B=2025, C=2026), the second is the month (A=Jan, B=Feb… L=Dec, Z=final stable), and the last two are the revision (0-9 then A-Z, where Z is highest). But before comparing dates, always check the binary level: the digit just before the date code (e.g. XXU9CZDP = Binary 9). You cannot downgrade to a lower binary level. If your device is on Binary 9, only flash Binary 9 or higher. Also make sure the 3-letter CSC code in the firmware matches your device region.
Download Samsung Galaxy S21 Ultra 5G SM-G998U Firmware
You can download the official stock firmware for your Samsung Galaxy S21 Ultra 5G SM-G998U directly from the links provided below. The most recent available build is the latest version. Once the download finishes, check that the file size matches the details listed in the table above. A mismatched file size usually indicates a corrupted or incomplete download, and attempting to flash a broken file will create additional software problems.
Only download firmware that is fully compatible with your exact device model. See the firmware selection guide above if you are not sure.
- Your model number is a variant of SM-G998U with a different letter suffix. Check About Phone carefully, one letter difference can cause a failed or broken flash.
- Your chipset differs from Qualcomm SM8350 Snapdragon 888 5G. Confirm in recovery mode before proceeding.
- You downloaded the file from a source other than this page.
- The file size differs significantly from the sizes listed in the table above, a size mismatch usually means a partial download, which will fail mid-flash.
Prerequisites for Samsung Galaxy S21 Ultra 5G SM-G998U Firmware
Preparing your computer and your phone before opening Odin prevents common errors like dropped connections or security locks. Two frequent issues with Samsung phones are a Samsung account that was not signed out, which can trigger KG lock, and a low-quality USB cable that drops the connection mid-flash. Always use a proper data cable, not a charge-only cable.
- Back Up IMEI Numbers: Dial *#06# and write down both IMEI numbers now. You will need these if you need to restore your IMEI after flashing.
- Remove Google Accounts: Sign out of all Google accounts to prevent FRP lock after flashing.
- Remove Samsung Accounts: Sign out of all Samsung accounts to avoid KG lock.
- Back Up Your Data: Back up everything, photos, contacts, WhatsApp chats, important files. Flashing wipes the device completely.
- Charge Your Device: At least 50% battery. A device that powers off during a flash is very difficult to recover.
- USB Cable & PC: Use a proper data USB cable, not a charge-only cable, and a Windows computer with available USB ports.
- Install Required Drivers:
How to Install Firmware on Samsung Galaxy S21 Ultra 5G SM-G998U
You can install the Samsung Galaxy S21 Ultra 5G SM-G998U firmware by loading the extracted AP, BL, CP, and CSC files into the Odin flash tool. We will use Odin for this process. A helpful tip: leave “Auto Reboot” and “F. Reset Time” checked in Odin to ensure the cleanest result. If you are uncertain about which Odin build to use, check our Odin versions page. Older Samsung phones occasionally function better with older Odin builds.
- Download and Extract:
- Download the correct firmware package from the links above.
- Extract the ZIP to a simple folder path, avoid paths with spaces or special characters, as some flash tools have trouble with them.
- Install the Listed Drivers:
- Confirm all drivers listed above are installed and that your PC has been restarted since installation. Skipping the restart is a common reason drivers do not work correctly.
- Load the Firmware File:
- In Odin, click “BL” and select the BL_*.tar.md5 file. Click “AP” and select the AP_*.tar.md5 file. Repeat for “CP” and “CSC”. Use HOME_CSC to keep data, or CSC for a clean flash.
- Connect Your Device:
- Enter Download Mode: Turn off your phone, then hold Volume Down + Power (add Home button on older models) until the warning screen appears. Press Volume Up to confirm and enter Download Mode.
- Connect your phone to your PC via USB. Odin should show “Added..” in the log area, this means your device is detected.
- Start Flashing:
- Click the “Start” button to begin.
- Do not disconnect, move the cable, or touch the device until the process is fully complete. Disconnecting mid-flash is how devices get bricked.
- Wait and Reboot:
- Once flashing finishes successfully, disconnect the device.
- Power on your device. The first boot will take longer than usual, give it up to 8 minutes.
Video Guide for Flashing
What to Expect After Flashing Samsung Galaxy S21 Ultra 5G SM-G998U Firmware
After applying the Samsung Galaxy S21 Ultra 5G SM-G998U firmware, your device will take several minutes to boot up and will be completely wiped of previous data. Many readers ask questions assuming something went wrong, so here is exactly what is normal after a successful flash:
- How to know the flash was successful: Odin will display “PASS.” in a green box near the top-left corner. Seeing this message means the installation completed properly.
- First boot takes 3 to 8 minutes, do not force the phone to restart. The system is rebuilding its core files. Interrupting this stage can cause a bootloop.
- The phone will feel warm during first boot, this is expected behavior. The device will cool down after the initial setup concludes.
- All your apps are gone, this is intentional. You will need to download them again from the Play Store. If you had Google backup enabled, the setup wizard will help you restore your applications.
- Dial *#06# immediately after setup to verify your IMEI status. Do this before inserting a SIM card. If the screen displays “unknown” or “null”, refer to the IMEI repair guide below to fix it.
- Be careful when re-adding your Google account, if you forgot to remove the account before flashing, an FRP prompt might appear. Enter your credentials directly through the setup wizard rather than the Settings menu.
- Wi-Fi, Bluetooth, and mobile data should function normally right away. If mobile data fails to connect, navigate to Settings › SIM and Network and input your APN details manually, as the flash can sometimes wipe carrier configurations.
- Stuck in a bootloop after first boot? Access recovery mode and execute a factory reset from there, see the hard reset guide above. This occasionally happens when old data conflicts with the new system and does not mean the firmware file is bad.
- Samsung Smart Switch: After flashing your Samsung Galaxy S21 Ultra 5G SM-G998U firmware, Samsung Smart Switch may prompt you to install additional updates. Let it complete, this ensures your device has the latest security patches for your region.
Missing IMEI or Corrupt Baseband on Samsung Galaxy S21 Ultra 5G SM-G998U After Flashing?
A missing IMEI after flashing the Samsung Galaxy S21 Ultra 5G SM-G998U usually indicates a corrupted EFS partition that requires specific repair tools. The EFS partition holds your IMEI and network data. Please note that writing a fake IMEI is illegal in most regions, so only use these tools to restore the original number that came with your phone. Software like ChimeraTool or BFT can assist with this process. Verify your local regulations before you begin.
Video Guide: How to repair IMEI
Common Issues When Flashing Samsung Galaxy S21 Ultra 5G SM-G998U
- Odin Shows “FAIL” Instead of “PASS”:
- This generally happens when the firmware region or model does not match your phone. Verify your exact model number under Settings › About Phone before selecting your files. A single letter difference in the model code is enough to cause a failure.
- Samsung Galaxy S21 Ultra 5G SM-G998U Not Recognized by Odin:
- Install the Samsung USB drivers again. Ensure the phone is actually in Download Mode. Try swapping to a different USB cable, as Odin requires a stable data connection.
- KG Lock / Knox Triggered After Flashing:
- This occurs when a Samsung account remains logged in prior to the flash, or if unofficial software was applied. Always sign out of Samsung accounts beforehand. If KG lock is already active, you typically need a specialized unlocking tool to resolve it.
- Boot Loop After Flashing:
- Open recovery mode (Volume Up + Power) and run a factory reset. This wipes away leftover data from the old system that might be causing the conflict.
Frequently Asked Questions
Q1: Will flashing the Samsung Galaxy S21 Ultra 5G SM-G998U firmware erase my data?
A: Yes, installing this firmware using Odin completely wipes the phone and restores the default Android 11, One UI 3.1 configuration. Every app, photo, contact, and account will be deleted. Save anything important before you begin, because data recovery is impossible once the process finishes.
Q2: Is this firmware compatible with other Samsung models?
A: No. This specific firmware is designed exclusively for the Samsung Galaxy S21 Ultra 5G SM-G998U equipped with the Qualcomm SM8350 Snapdragon 888 5G processor. Even a Galaxy S21 Ultra 5G with a slightly different letter suffix can feature entirely different internal hardware. Forcing the wrong firmware onto a phone can leave it severely damaged. Always verify your exact model in Settings › About Phone.
Q3: Can I downgrade from the latest version to an older firmware version?
A: While technically possible on certain Qualcomm devices, I advise against it. Rolling back can introduce security vulnerabilities and break app compatibility on Android 11, One UI 3.1. If the newest build is giving you trouble, leave a comment below, as there is usually a safer alternative to downgrading.
Q4: What should I do if I encounter an FRP lock after flashing?
A: Use our free Android apps launcher. FRP activates on the Samsung Galaxy S21 Ultra 5G SM-G998U if a Google account was left signed in prior to the flash. This is why removing your Google account beforehand is the best practice to prevent the lock entirely.
Q5: Are custom ROM options available for the Samsung Galaxy S21 Ultra 5G SM-G998U?
A: This page focuses entirely on official Samsung stock software. The availability of custom ROMs for the Samsung Galaxy S21 Ultra 5G SM-G998U relies on whether the Qualcomm SM8350 Snapdragon 888 5G chipset has open-source kernel support. You can check our Custom ROMs page or visit the XDA Developers forum for specific custom development threads.
Q6: My Samsung Galaxy S21 Ultra 5G SM-G998U is not detected by Odin. What should I do?
A: Start by reinstalling the Samsung USB drivers and rebooting your computer. Try moving the cable to a USB 2.0 port instead of a USB 3.0 port, as Samsung phones often communicate more reliably over USB 2.0. Temporarily disable your antivirus software. If the problem persists, leave a comment with the exact error message and I will assist you further.
Q7: How do I enter recovery mode on my Samsung Galaxy S21 Ultra 5G SM-G998U?
A: Turn the phone completely off, then press and hold Volume Up + Power together until the recovery menu loads. If you are using an older Samsung phone with a physical Home button, press Volume Up + Home + Power. The recovery screen will show the build number for your Samsung Galaxy S21 Ultra 5G SM-G998U, which helps you verify your software version before flashing.
Q8: My IMEI shows “unknown” after flashing the Samsung Galaxy S21 Ultra 5G SM-G998U. Is my phone permanently damaged?
A: No, the phone is not ruined, and the issue is repairable. Follow the IMEI repair guide located in the troubleshooting section above. For Samsung phones, always inspect the EFS partition for corruption first. Remember not to insert a SIM card until the IMEI is successfully restored.
Q9: How long does it take to flash Samsung Galaxy S21 Ultra 5G SM-G998U firmware?
A: The actual installation inside Odin typically requires 3 to 10 minutes, depending on the file size and your USB transfer speed. The initial boot after the flash takes additional time, usually between 3 and 8 minutes. Do not unplug or restart the phone during either phase. If the Odin progress bar seems frozen, wait a few extra minutes before assuming there is an error.
Final Thoughts on Samsung Galaxy S21 Ultra 5G SM-G998U Firmware
Following this guide carefully will result in a successful flash of the Samsung Galaxy S21 Ultra 5G SM-G998U firmware and a fully functional device. If you followed the instructions accurately, your phone should now operate on a clean, official software build.
If you ran into an unexpected error or a specific step did not work, leave a comment below. Provide as much detail as possible, including the exact error message, the step you are currently on, and the troubleshooting steps you have already attempted. I read every comment and will help you resolve the issue.
If you found this tutorial helpful, please share it with others who might be facing the same situation.
Browse all Samsung firmware downloads for more devices.
Disclaimer: Flashing stock firmware is performed at your own risk. Follow the instructions on this page carefully. I cannot be held responsible for any damage to your device, but I will always try to help if something goes wrong.
