Quick fix: Open Command Prompt (Admin). Run: vssadmin list shadowstorage to see current allocation. To resize: vssadmin resize shadowstorage /for=C: /on=C: /maxsize=20GB. This caps shadow storage at 20GB. To remove cap: use /maxsize=UNBOUNDED. Shadow copies older than the cap auto-delete.

Shadow Copy (Volume Shadow Copy Service) creates point-in-time snapshots of disk content. Used by System Restore, File History’s Previous Versions, Backup software. Allocation is fixed by default (~10% of drive). On big drives that’s wasteful; on small drives it’s not enough. Adjust via vssadmin.

Symptom: Want to adjust how much disk space Shadow Copies (System Restore points) can use.
Affects: Windows 11 (and Windows 10/Server editions).
Fix time: ~5 minutes.

What causes this need

Shadow Copy storage defaults to ~10% of the disk (capped). On a 1TB drive that’s 100GB — potentially excessive. On a 256GB SSD with limited space, even 25GB is significant. Tuning the cap balances: keeping useful restore points vs reclaiming space.

Method 1: List and resize via vssadmin

The standard route.

Open Command Prompt as Admin.
List current shadow storage:
```
vssadmin list shadowstorage
```
Output:
- Used Shadow Copy Storage space: currently used.
- Allocated Shadow Copy Storage space: reserved.
- Maximum Shadow Copy Storage space: max allowed.
Resize:
```
vssadmin resize shadowstorage /for=C: /on=C: /maxsize=20GB
```
This caps at 20GB. Older shadows beyond cap auto-delete.

For unlimited:

vssadmin resize shadowstorage /for=C: /on=C: /maxsize=UNBOUNDED

For removing all current shadows: vssadmin delete shadows /for=C: /all.
For listing existing shadow copies: vssadmin list shadows.

This is the standard usage.

Method 2: Manage via System Protection settings

For UI approach.

Open System Properties: Win+R → SystemPropertiesProtection.
Or: Settings → System → About → System protection.
Under Protection Settings: pick the drive you want to manage.
Click Configure.
Under Max Usage: slider sets percentage of disk used.
Adjust slider. Click Apply.
For deleting all restore points: click Delete. Confirms current shadow copies removed.
For turning off System Restore on a drive: pick “Disable system protection.” All shadows removed.
This UI sets the same vssadmin cap behind the scenes.

This is the GUI approach.

Method 3: PowerShell for automation

For scripting.

PowerShell wraps vssadmin. Run as Admin:
```
Get-WmiObject -Class Win32_ShadowStorage
```
Lists allocated/used/max for each drive.

Or via cmdlet:

Get-CimInstance -ClassName Win32_ShadowStorage

To resize via PowerShell (uses vssadmin internally):
```
vssadmin resize shadowstorage /for=C: /on=C: /maxsize=15GB
```
(invoked from PowerShell same as cmd)

For getting list of current snapshots:

Get-WmiObject -Class Win32_ShadowCopy | Select-Object ID, DeviceObject, InstallDate

To delete specific snapshot:

(Get-WmiObject -Class Win32_ShadowCopy | Where-Object { $_.ID -eq "{ID}" }).Delete()

For scheduled cleanup: Task Scheduler runs script weekly to delete shadows older than 30 days.

This is the scripting approach.

How to verify the fix worked

vssadmin list shadowstorage shows the new maxsize.
Disk free space increases (if you reduced the cap).
System Protection → Configure shows the updated slider position.
System Restore still works: create a restore point and verify.

If none of these work

If vssadmin fails: Permission: must run as Admin. Drive can’t hold the new size: drive too small. Reduce maxsize. Storage not present: shadow storage not allocated yet. Use vssadmin add shadowstorage /for=C: /on=C: /maxsize=15GB to create it. System Restore disabled: re-enable in System Protection. For corrupted VSS: Services.msc → Volume Shadow Copy → Restart. Or re-register: vssadmin list providers → re-add. For backup software conflicting: Veeam, Acronis, Macrium may manage shadow storage. Coordinate cap. For drive too full: shadow storage can’t allocate. Free disk space first.

Bottom line: vssadmin resize shadowstorage /for=C: /on=C: /maxsize=20GB in Admin cmd. Or System Protection slider in System Properties. Balances disk space vs available restore points.