Is it safe to delete the EFI System Partition?

No, don't delete the EFI System Partition your PC boots from. It holds the Windows Boot Manager and the files your firmware loads at startup. Without it, Windows won't start. It's also tiny, so deleting it would never solve a full disk anyway. The only EFI partition you can remove is a leftover one on another drive that nothing boots from any more.

Quick verdict:

• Never: the EFI partition on the drive Windows boots from.
• Careful: on a dual-boot PC, the same partition usually holds Linux's boot loader too.
• Usually OK: a leftover EFI partition on an old or second drive, once you've confirmed the PC boots without it.
• Not worth it for space: it's a few hundred megabytes at most.

What is the EFI System Partition?

On a PC with UEFI firmware, which includes every PC that meets Windows 11's requirements, the drive Windows boots from uses a GPT partition table and has a small EFI System Partition (ESP). Microsoft's partition guidelines describe it as the partition the device boots to, formatted FAT32, managed by the operating system, and kept free of anything else.

Inside it you'll find the EFI folder with Microsoft\Boot (the Windows Boot Manager and its BCD store) and Boot\bootx64.efi, the fallback boot file. Other systems add their own folders here: a Linux install typically adds one for its boot loader, such as EFI\ubuntu.

The partition has no drive letter, so you won't see it in File Explorer. In Disk Management (right-click Start) it shows as a small EFI System Partition at the start of the disk, next to a Recovery Partition. The default layout is: EFI System Partition, Microsoft Reserved Partition (MSR, which Disk Management doesn't show), Windows, Recovery.

How much space does it use?

Very little. Microsoft's current minimum is 200 MB on most drives and 300 MB on 4K-native drives, and many older PCs have a 100 MB ESP. You can see the exact size in Disk Management.

So if your drive is full, the EFI partition isn't the cause. To find out what is, scan the drive with a disk analyzer: SquirrelDisk lists your drives on the home screen, and once you pick one it shows which folders take the space. The EFI partition has no drive letter and isn't something you'll need to scan.

When can an EFI partition be removed?

Typical cases where an extra ESP is left behind:

• You cloned or moved Windows to a new SSD, and the old drive is now a data drive but still has its old EFI and Recovery partitions.
• A second drive once had Windows or Linux installed on it.
• You removed Linux from a separate drive and its ESP stayed.

Check that nothing boots from it

1. Open Disk Management and note which disk holds C: and which disk holds the extra EFI partition.
2. Shut down, disconnect the old drive (or disable it in the firmware settings), and start the PC. If Windows starts normally, it doesn't need that drive's ESP.
3. Make sure you don't use the old drive to start another system, such as Linux or an older Windows, from the firmware's boot menu.
4. Back up anything you want to keep from that drive.

Delete it with DiskPart

Disk Management deliberately doesn't let you delete an EFI System Partition. DiskPart can, with the override option, which Microsoft describes as letting it delete any partition regardless of type. There's no undo and no Recycle Bin, so read each line before you press Enter.

1. Right-click Start, open Terminal (Admin) and type diskpart.
2. Type list disk and find the old drive by its size. Double-check: picking the wrong disk here is how people lose their boot partition.
3. Type select disk 1, using the number of the old drive.
4. Type list partition. The ESP is the small one of type System.
5. Type select partition 1, using the number of that partition.
6. Type delete partition override.
7. Type exit.

If DiskPart refuses, it's often because that partition is in use as the system partition. Stop there: it means Windows is booting from it.

Using the freed space

The ESP is usually at the start of the disk. Disk Management can only extend a volume into free space that comes after it, so you often can't add those few hundred megabytes to the existing data partition. You can create a small new volume there, or simply leave it. If you're repurposing the whole drive and have backed it up, DiskPart's clean command on that disk removes every partition at once, after which you can create one new volume in Disk Management.

What you should not delete

• The ESP on your Windows drive. Even if you have two, the one Windows is using must stay. If you're not sure which is which, don't delete either.
• The ESP on a dual-boot PC. Windows and Linux often share one ESP on the same drive. Deleting it breaks both. If you removed Linux, its leftover folder inside the ESP takes very little space; leaving it is the safe choice.
• The Recovery and MSR partitions next to it on your Windows drive. They're needed for Windows' recovery tools and partition management.
• Files inside the ESP. Don't mount it with a drive letter to clean it out. A missing file there can stop Windows from starting.

If you deleted the wrong one

Your files on C: are still there, but Windows won't start until the boot files are back. Start from Windows installation media, choose Repair your computer, and open a Command Prompt (or press Shift+F10 in Setup). There you can recreate a FAT32 system partition with DiskPart and copy the boot files back with bcdboot, as described in Microsoft's BCDBoot documentation. If BitLocker is on, have your recovery key ready. If that sounds daunting, ask someone experienced to help before you try anything else on the drive.

Better ways to free space

The partitions around Windows are small. The big wins are almost always inside C:: an old Windows installation after an upgrade (is it safe to delete Windows.old), update leftovers (the SoftwareDistribution folder), and your own files. A scan with SquirrelDisk shows which folders those are, so you can decide what to remove.