Windows 11 Missing From GRUB? Here’s How to Bring It Back

You installed Ubuntu next to Windows 11, and everything looked fine at first. Then after an update or a fresh install, you restarted your PC and Windows 11 was gone from the GRUB menu. Only Ubuntu shows up. This is a very common dual boot problem, and in most cases Windows is still safe on your disk.

The issue is usually not damage. GRUB simply stopped detecting the Windows bootloader. Once you help GRUB find it again, the Windows entry comes back and you can boot both systems normally.

Quick Answer

Boot into Ubuntu, open a terminal, and run sudo os-prober to check if Windows is detected. If it is, make sure os-prober is enabled in /etc/default/grub by adding GRUB_DISABLE_OS_PROBER=false, then run sudo update-grub. Restart your PC and Windows 11 should appear in the GRUB menu again.

Why Windows 11 Disappears From GRUB

GRUB is the bootloader that lets you choose an operating system at startup. To show Windows in the menu, GRUB needs to find the Windows Boot Manager file on your EFI partition.

There are several reasons this can fail.

1. os-prober Is Disabled

Since Ubuntu 22.04, os-prober is disabled by default for security reasons. os-prober is the tool that scans other partitions for operating systems. If it is off, update-grub will only list Ubuntu and ignore Windows completely.

2. Fast Startup Is Enabled in Windows

Windows Fast Startup does not fully shut down the system. It hibernates part of the system instead. This can lock the Windows partition and make it invisible or unsafe for Linux tools to read.

3. The EFI Partition Was Changed

A BIOS update, a Windows update, or installing Ubuntu in a different boot mode can change the EFI System Partition. If Ubuntu was installed in Legacy mode while Windows uses UEFI mode, GRUB cannot chainload Windows properly.

4. GRUB Was Not Updated After Install

Sometimes the installer finishes but GRUB is not regenerated correctly. A simple manual update fixes this.

Before You Start: Check Your Boot Mode

Both Windows and Ubuntu must use the same boot mode, ideally UEFI. To check how Ubuntu booted, run this command:

[ -d /sys/firmware/efi ] && echo "UEFI mode" || echo "Legacy mode"

If it says UEFI mode, you are good. If it says Legacy mode and your Windows 11 uses UEFI, you should reinstall Ubuntu in UEFI mode or convert the boot setup. Windows 11 officially requires UEFI, so this mismatch is a red flag.

Also check that your Windows partition still exists:

sudo fdisk -l

Look for NTFS partitions and a small FAT32 EFI partition, usually 100 to 500 MB in size.

Step-by-Step Fix: Enable os-prober and Update GRUB

Follow these steps in order. Most users fix the problem here.

1. Boot into Ubuntu and log in normally.
2. Open a terminal with Ctrl + Alt + T.
3. Install os-prober if it is missing: sudo apt update && sudo apt install os-prober
4. Test detection: sudo os-prober. You should see a line mentioning Windows Boot Manager.
5. Open the GRUB config file: sudo nano /etc/default/grub
6. Add or edit this line: GRUB_DISABLE_OS_PROBER=false
7. Save the file with Ctrl + O, press Enter, then exit with Ctrl + X.
8. Regenerate GRUB: sudo update-grub
9. Watch the output. It should say it found Windows Boot Manager.
10. Restart: sudo reboot

When your PC restarts, the GRUB menu should now list both Ubuntu and Windows Boot Manager. Select Windows to test it.

For more background on how GRUB configuration works, the official Ubuntu GRUB2 documentation explains the config files in detail.

Fix 2: Mount the EFI Partition and Reinstall GRUB

If os-prober finds Windows but the menu still does not show it after a reboot, reinstalling GRUB often helps.

1. Find your EFI partition: lsblk -f. It is usually /dev/sda1 or /dev/nvme0n1p1 and formatted as FAT32.
2. Mount it if it is not mounted: sudo mount /dev/nvme0n1p1 /boot/efi — replace the device name with yours.
3. Reinstall GRUB for UEFI: sudo grub-install --target=x86_64-efi --efi-directory=/boot/efi --bootloader-id=ubuntu
4. Update GRUB again: sudo update-grub
5. Reboot and check the menu.

This rebuilds the Ubuntu entry in your firmware boot list and refreshes the GRUB files.

Fix 3: Disable Fast Startup in Windows

If you can still boot Windows from your BIOS boot menu (often by pressing F12, F8, or Esc at startup), disable Fast Startup. It causes many dual boot issues.

1. Boot into Windows 11.
2. Open Control Panel and go to Power Options.
3. Click “Choose what the power buttons do.”
4. Click “Change settings that are currently unavailable.”
5. Uncheck “Turn on fast startup.”
6. Save changes and shut down fully — do not restart, shut down.
7. Power on and boot Ubuntu, then run sudo update-grub again.

While you are in Windows, also run a full shutdown once from Command Prompt with shutdown /s /f /t 0 to clear any hibernation state.

Fix 4: Add a Manual GRUB Entry for Windows

If os-prober still fails, you can add Windows manually. This is a reliable backup method.

1. Find the UUID of your EFI partition: sudo blkid | grep -i efi
2. Open the custom GRUB file: sudo nano /etc/grub.d/40_custom
3. Add these lines at the end, replacing YOUR-UUID with the real UUID:
   
   menuentry "Windows 11" {

insmod part_gpt

insmod fat

search --no-floppy --fs-uuid --set=root YOUR-UUID

chainloader /EFI/Microsoft/Boot/bootmgfw.efi

}
4. Save the file and run sudo update-grub.
5. Reboot and test the new Windows 11 entry.

If you enjoy working with Ubuntu from the command line, our guide on how to update Ubuntu from the terminal covers the essential maintenance commands every dual boot user should know.

Fix 5: Check BIOS Boot Order

Sometimes GRUB is fine, but your firmware boots Windows or Ubuntu directly and skips the menu. Enter your BIOS or UEFI settings and make sure “ubuntu” is the first boot option. Then GRUB will load first and show you the choice.

You can also check the boot order from Ubuntu:

efibootmgr -v

To set Ubuntu first, use: sudo efibootmgr -o XXXX,YYYY where XXXX is the boot number for Ubuntu shown in the list.

If GRUB loads but hides the menu too quickly, edit /etc/default/grub and set GRUB_TIMEOUT_STYLE=menu and GRUB_TIMEOUT=10, then run sudo update-grub again.

Common Mistakes and Useful Tips

• Running update-grub without enabling os-prober: On newer Ubuntu versions this will never add Windows. Always set GRUB_DISABLE_OS_PROBER=false first.
• Editing the wrong file: Never edit /boot/grub/grub.cfg directly. It gets overwritten. Edit /etc/default/grub or /etc/grub.d/40_custom instead.
• Using the wrong EFI partition: On systems with two drives, each drive may have its own EFI partition. Use the one that contains the EFI/Microsoft folder.
• Forgetting to disable Secure Boot issues: If GRUB fails to load after changes, check that Secure Boot is either on with signed Ubuntu bootloader or temporarily disabled for testing.
• Tip: After fixing the issue, back up your working GRUB config with cp /boot/grub/grub.cfg ~/grub-backup.cfg so you can compare later.
• Tip: Keep a live Ubuntu USB nearby. If GRUB breaks completely, you can boot from USB and repair it with Boot-Repair.

The Boot-Repair tool is another popular option. You can read about its usage in the Ubuntu community Boot-Repair guide, but try the manual steps above first — they solve most cases without extra software.

Conclusion

A missing Windows 11 entry in GRUB looks scary, but your Windows install is almost always still intact. In most cases, enabling os-prober and running sudo update-grub brings the entry back in under five minutes. If that fails, disabling Fast Startup, reinstalling GRUB to the correct EFI partition, or adding a manual menu entry will fix it. Work through the steps in order, reboot to test after each fix, and you will have a clean dual boot menu again where both Ubuntu and Windows 11 are just one key press away.

Frequently Asked Questions

Will running update-grub delete my Windows files?

No. The update-grub command only rebuilds the GRUB menu configuration. It does not touch your Windows partition, your personal files, or the Windows bootloader itself.

Why did Windows disappear after an Ubuntu update?

A kernel or GRUB package update regenerates the GRUB menu. If os-prober is disabled by default in that version, Windows is not added back during regeneration. Enabling os-prober prevents this from happening again.

Can I boot Windows if GRUB does not show it?

Yes. Use your PC’s one-time boot menu, usually F12 or Esc during startup, and select Windows Boot Manager. This boots Windows directly and is a good way to disable Fast Startup.

What if os-prober finds nothing at all?

Check that the EFI partition is mounted and that your Windows drive is detected with lsblk. Also disable Fast Startup and fully shut down Windows. If the drive itself does not appear, check cables, BIOS settings, and disk health.

Should I use Boot-Repair or fix GRUB manually?

Try the manual fix first because it is simple and you learn exactly what changed. Use Boot-Repair if GRUB itself will not load, or if you have a complex setup with multiple drives and operating systems.