>

Check a drive for file system errors with chkdsk

Diagnose NTFS file system errors and bad sectors on any volume — including the system drive while Windows is running — before committing to a repair.

WindowsFilessystemDiagnosticsLow risk
Run `chkdsk C: /scan` for an online, read-only diagnostic scan; only escalate to `chkdsk C: /f /r` when errors are actually reported.

01Command

Command
$ chkdsk C: /scan

02What it does

Without switches chkdsk inspects the volume in read-only mode and reports problems without touching anything. The /scan switch performs a full online scan on NTFS volumes without dismounting, so you can keep working on the system drive. If the scan reports errors, repair with `chkdsk C: /f` (file system fixes, requires a restart for the system drive) and add /r to also locate bad sectors and recover readable data — the latter can take hours on large drives. Recovery of lost file fragments lands in folders like `FOUND.000` at the drive root.

03Risk

RiskLow risk
RequirementsRead-only online scan needs no elevation; repairing with /f or /r requires admin and exclusive disk access.
!Warning: Run /f and /r fixes only after backing up important data: repairing severe file system damage can surface previously hidden lost clusters as FOUND.000 fragments.

04Undo

✓No undo needed — this command does not change persistent state.

05Sources

  • chkdsk | Microsoft Learn
    Microsoft · vendor-doc · 2026-09-17
    Evidence: Microsoft documents chkdsk /scan as running an online scan on a volume, and /f with /r as locating bad sectors and recovering readable information.
  • Check Disk - chkdsk - Windows CMD
    SS64 · technical · 2026-09-17
    Evidence: SS64 explains that chkdsk without switches runs in read-only mode, while /f fixes errors found on the disk.

Last verified: 2026-09-17 · Category: System & Settings

06Related solutions

Scan and repair Windows system files with SFC
WindowssystemTerminalDiagnostics

Use the System File Checker to verify every protected Windows system file against known-good copies and automatically replace the damaged ones.

Low risk ✓ 2026-09-17
Mirror folders with robocopy for exact backups
WindowsFilessystemTerminal

Robocopy is Windows' built-in robust file copier: use /MIR to keep a destination folder as an exact one-way mirror of a source, resumable and restartable.

High risk ✓ 2026-09-17
Repair the Windows component store with DISM RestoreHealth
WindowssystemTerminalDiagnostics

Use the Deployment Image Servicing and Management tool to detect and repair corruption in the Windows component store, the layer SFC depends on.

Medium risk ✓ 2026-09-17