CHKDSK: The Check Disk Utility in Windows

What CHKDSK does

CHKDSK verifies the logical integrity of a file system (NTFS, FAT32, exFAT) by checking directory entries, security descriptors, and cluster allocation. With the /r switch it also scans the physical disk surface for bad sectors and attempts to recover readable data from damaged areas before marking them unusable.

Run without any switches, chkdsk performs a read-only report: it lists file system errors it finds but changes nothing on disk unless you add a repair switch such as /f, /r, /scan, or /spotfix.

Read-only scan vs. repair

chkdsk C: alone is always safe to run — it opens the volume for read access, walks the file system metadata, and prints a summary without writing anything. Adding /f, /r, /x, or /spotfix switches chkdsk into repair mode: it needs exclusive or near-exclusive access to the volume and will fix (or attempt to fix) whatever it finds. Use the read-only pass first if you just want to know whether a drive has problems before committing to a repair run.

Full switch reference

Basic syntax

Run these from an elevated Command Prompt or Windows Terminal. Replace C: with the drive letter you want to check; /i, /c, and /l:size only apply to NTFS volumes.

chkdsk
chkdsk C:
chkdsk C: /f
chkdsk C: /r
chkdsk C: /scan
chkdsk C: /spotfix
chkdsk C: /f /r /x

Running CHKDSK from Windows

1. 1Click Start, type cmd, and choose 'Run as administrator' (or open an elevated Windows Terminal).
2. 2Type chkdsk C: and press Enter for a read-only report, or add /f or /r for a repair pass.
3. 3Alternatively, right-click the drive in File Explorer, open Properties > Tools, and click Check — this runs the same engine through a graphical wrapper.

Running CHKDSK from an elevated prompt at boot

When you run chkdsk /f, /r, or /x against the drive Windows is currently booted from, Windows can't lock that volume while it's in use, so it schedules the check for the next restart instead of running immediately. Answer Y when prompted, then restart; the scan runs before Windows fully loads, showing progress through several numbered stages on a blue console-style screen.

The 'volume is in use' schedule-at-restart flow

1. 1Run chkdsk C: /f (or /r) from an elevated prompt against your system drive.
2. 2Windows reports it cannot lock the volume because it is in use and asks: 'Would you like to schedule this volume to be checked the next time the system restarts? (Y/N)'.
3. 3Type Y and press Enter to queue the scan.
4. 4Restart the PC; the scan runs automatically before the desktop loads.
5. 5If you change your mind before restarting, run chkntfs /x C: to cancel the scheduled scan for that drive.

Running CHKDSK from recovery media

1. 1Boot from Windows installation media or Windows Recovery Environment (WinRE) and choose Repair your computer.
2. 2Go to Troubleshoot > Advanced options > Command Prompt.
3. 3Identify the correct drive letter for Windows — it's often not C: in WinRE, since the recovery environment assigns letters differently. Use diskpart's list volume command to confirm.
4. 4Run chkdsk against that drive letter with the switches you need, for example chkdsk D: /f /r.
5. 5This is the only way to repair the system volume when Windows won't boot far enough to schedule an on-restart scan itself.

How long CHKDSK takes, and why it looks stuck

A read-only scan or /f pass typically finishes in a few minutes on a healthy drive. Adding /r can take from a few minutes on a small SSD to many hours on a large mechanical drive, because it physically reads every sector. chkdsk can appear frozen at the same percentage for a long stretch — this is normal during the bad-sector scan stages, since progress slows wherever damaged sectors are clustered rather than moving at a steady rate. Only treat it as truly hung if there's been no disk activity (no light, no sound) for several hours.

CHKDSK on SSDs

SSDs have no moving parts, so mechanical 'bad sectors' don't apply, but the NAND flash controller can still develop failing blocks and the file system layer can still get corrupted after a crash or power loss. Running chkdsk /scan or /f on an SSD is safe and useful; avoid running it obsessively, since repair passes cause writes and SSDs have finite write endurance. /r is rarely worth running on an SSD, since bad-block remapping is already handled internally by the drive's own controller — prefer /scan followed by /spotfix if problems are found.

Risks and when NOT to run CHKDSK

• If a drive is making clicking or grinding noises, or is intermittently not detected, back up data first — a repair pass on physically failing hardware can worsen corruption or make recovery harder.
• Don't run /r as a routine habit on a healthy SSD; it adds unnecessary writes for no benefit.
• If Windows reports the file system as RAW, chkdsk cannot help — there is no recognized file system for it to check. Try file recovery software before reformatting.
• If you need to recover deleted or lost files, don't run a repair pass first; recovery software reads the drive without altering it, while chkdsk can convert unreadable fragments into .chk files, changing their location.
• CHKDSK does not repair corrupted Windows system files — that's the job of System File Checker and DISM, not disk-level repair.

Reading the results in Event Viewer

1. 1Open Event Viewer (eventvwr.msc).
2. 2Expand Windows Logs > Application.
3. 3Filter by source 'Wininit' — chkdsk logs its results under this source after a scheduled boot-time scan (older versions used a source named 'Chkdsk').
4. 4Open the most recent matching event, typically Event ID 1001 or 26226, to read the full report, including bad sector counts and files recovered.