Quick fix: CHKDSK on the system drive (C:) requires reboot because Windows holds it open. For non-system drives (D:, E:, USB): can run without reboot if no apps have files open. Close all apps on target drive, then chkdsk D: /f in Terminal (Admin) runs immediately. For C:: schedule for next reboot via chkdsk C: /f /scan (online repair).

CHKDSK is Windows’s disk error-check tool. Standard usage requires reboot when checking system drive. For other drives, immediate scan. Online scanning option also runs while Windows is up.

Symptom: Want to run CHKDSK without rebooting the system.
Affects: Windows 11 (and Windows 10).
Fix time: ~5 minutes + scan time.

What causes this

CHKDSK locks the volume during scan. System drive (C:) is constantly in use by Windows; can’t lock. Standard CHKDSK schedules to run at next boot before Windows loads. Non-system drives can be locked if no apps have files open. Modern Windows also supports online scan that doesn’t need lock.

Method 1: Run CHKDSK on non-system drive immediately

The simple case.

Open Terminal (Admin).
Close apps using the target drive. Especially: File Explorer windows open at it.
Run:
```
chkdsk D: /f
```
The /f flag fixes errors. Without /f: read-only check.
If still locked: chkdsk D: /f /x. /x dismounts the volume forcibly.
For full surface scan (bad sectors): chkdsk D: /f /r. Takes hours.
For network drive: not directly supported. Mount as local first.

Standard chkdsk for non-system drives.

Method 2: Online scan for system drive

For C: without reboot.

Open Terminal (Admin).
Run online scan (no reboot needed):
```
chkdsk C: /scan
```
This is read-only verification. Reports errors but doesn’t fix.
For online repair (NTFS only):
```
chkdsk C: /scan /forceofflinefix
```
Marks errors found during online scan; fixes queued for next reboot.
To run queued offline fixes during current session (no boot wait):
```
chkdsk C: /spotfix
```
Fixes only specific marked errors. Requires brief volume lock.
Combined: chkdsk C: /scan for read-only check. chkdsk C: /spotfix only when errors are found and you want to fix without full offline scan.

Online scan is the right path for C: without reboot.

Method 3: Use PowerShell Repair-Volume for managed approach

For modern scripting.

Open Terminal (Admin).
Quick scan (online):
```
Repair-Volume -DriveLetter C -Scan
```
Online repair attempt:
```
Repair-Volume -DriveLetter C -SpotFix
```

Full offline repair (schedules for reboot):

Repair-Volume -DriveLetter C -OfflineScanAndFix

For all drives at once:
```
Get-Volume | Repair-Volume -Scan
```
Output gives status: NoErrorsFound, Spotfix, OfflineScanAndFix.

PowerShell is the modern API.

How to verify the fix worked

chkdsk completes with summary: total bytes, errors found, errors fixed.
Windows has checked the file system and found no problems. = healthy.
Event Viewer → Windows Logs → Application → filter for source Wininit shows chkdsk results.

If none of these work

If errors persist: Bad sectors: NTFS marks bad sectors. Drive may be failing. SMART check via CrystalDiskInfo. For drives with frequent errors: dying drive. Backup data, replace. For locked volume that won’t dismount: a service or process is using it. Open Resource Monitor → CPU tab → Search Handles → type drive letter to find process. Kill, retry. For chkdsk that finds errors but won’t fix: /forceofflinefix marks for next reboot. For very fast SSDs that chkdsk seems redundant: SSDs have internal error correction. chkdsk less useful than for HDD. Run quarterly or after suspect events.

Bottom line: Non-system drives: chkdsk D: /f runs immediately. System drive: chkdsk C: /scan for online check, chkdsk C: /spotfix for targeted fix without full reboot. PowerShell Repair-Volume is the modern API.