Does CHKDSK fix bad sectors?

CHKDSK is a command-line utility built into Windows that checks the file system and disk surface for errors. It can detect bad sectors, but it does not actually repair them. CHKDSK can only mark bad sectors as unusable so that data is not stored on them. To truly fix bad sectors, more advanced disk repair utilities need to be used.

What CHKDSK Does

CHKDSK examines the logical file system structure on a drive and looks for inconsistencies that could indicate corruption or damage. Some examples of errors it detects include:

  • Cross-linked files and folders
  • Incorrect folder hierarchies
  • Invalid files
  • Bad sectors

When CHKDSK encounters these types of errors, it will take steps to repair the file system structure. For instance, it can:

  • Remove invalid file entries
  • Move incorrectly placed files back to the proper location
  • Reconnect improperly linked files or folders
  • Mark bad sectors as unusable

These repairs aim to restore integrity and consistency to the file system indexing so that files can be properly located and accessed again. However, CHKDSK does not actually extract data from bad sectors or attempt to repair them at a physical level.

Bad Sector Detection

One of the checks CHKDSK performs is scanning the disk surface for bad sectors. These are physical areas on the hard disk platters that have become inaccessible because they are physically damaged or unstable. Typical causes include:

  • Manufacturing defects
  • Overheating
  • Physical trauma like drops or impacts
  • Mechanical failure
  • Electrical issues
  • Magnetic interference

Bad sectors can develop over time as a result of normal wear and tear or acute damage. The sectors may become completely unreadable or only intermittently accessible. As long as bad sectors are limited in number, the drive remains fully functional.

CHKDSK will detect bad sectors because it will be unable to access the data stored on them during its surface scan. It will then mark them in the file system so no further data gets written there. This prevents data loss or corruption since the bad areas are essentially quarantined. However, the bad sectors themselves are not repaired.

Marking Bad Sectors

CHKDSK does not physically fix bad sectors found during its checks. Instead, it logs their locations and makes a note in the file system accounting structures. The bad sector information gets recorded in two places:

  • The S.M.A.R.T. (Self-Monitoring, Analysis and Reporting Technology) data on the drive
  • The file allocation table (FAT or MFT)

The S.M.A.R.T. diagnostic data provides technical information about drive health and reliability for monitoring purposes. When CHKDSK marks sectors bad, it gets accounted for in the overall S.M.A.R.T. assessment of the disk.

Marking bad sectors in the FAT or MFT prevents files from being allocated there. The file system simply skips over them when writing data so that bad areas are avoided. This isolates bad sectors to protect data integrity.

While quarantining bad sectors helps limit further issues, it does not resolve the underlying damage. The bad areas themselves remain on the disk. To physically repair bad sectors requires more specialized tools.

Repairing vs. Marking Bad Sectors

There is an important distinction between just marking bad sectors like CHKDSK does and actually repairing them. True bad sector repair writes corrected data back to the problematic areas to improve read/write functionality.

Repairing bad sectors is challenging because it requires very low-level access to the physical drive in order to rewrite the magnetic data. Specialized hard drive repair tools are able to directly access the disk platters and diagnose and correct bad areas. They can perform functions like:

  • Extracting data from damaged sectors using advanced read methods
  • Writing repaired data patterns back to unstable sectors
  • Filling in bad regions with magnetic placeholders to stabilize them
  • Remapping bad sectors to spare sectors in case of unrecoverable physical damage

This type of physical disk repair maximizes the usable space on the drive by restoring the maximum number of sectors. The more bad sectors that can be fixed, the less chance of data loss or performance issues.

When To Use CHKDSK vs. Repair Tools

CHKDSK is generally recommended as a first response if your hard drive starts behaving strangely or shows signs of damage. Running CHKDSK can often resolve file system problems and mark down any bad areas.

However, if the issues persist after CHKDSK, it’s a sign that you have physical bad sectors that need repairs beyond just marking. At that point, you should use advanced hard drive repair tools to further diagnose the drive health and perform low-level repairs.

Repair utilities like SpinRite or HDDSuperClone can interface with the disk hardware directly to recover data from bad sectors and attempt to repair them. This gives you the best chance of restoring damaged drives to full health.


In summary, CHKDSK does not actually fix bad sectors itself, but it can detect and mark bad areas to prevent their use. This helps preserve data integrity and limit further problems. True bad sector repair requires specialized tools that can access the disk platters at a very low level to extract data and rewrite damaged regions. CHKDSK is a good starting point, but for full bad sector repairs, advanced hard drive repair software is necessary.

Frequently Asked Questions

What are bad sectors?

Bad sectors are portions of a hard disk that have become inaccessible due to physical damage or corruption. They develop over time or can occur from sudden trauma. Bad sectors may be completely unreadable or only intermittently accessible.

What causes bad sectors?

Common causes of bad sectors include manufacturing defects, overheating, physical impacts, mechanical failure, electrical issues, magnetism, and normal wear and tear over time.

How can I tell if I have bad sectors?

Symptoms of bad sectors may include computer crashes, slow performance, file corruption, and inability to access portions of a drive. Running CHKDSK or a SMART utility can detect bad sectors.

What does CHKDSK do when it finds bad sectors?

CHKDSK logs and marks any bad sectors it encounters so that the file system avoids writing data there in the future. This isolates bad areas but does not repair them.

Can CHKDSK actually fix bad sectors?

No, CHKDSK cannot truly fix bad sectors at the physical level. It marks bad areas as unusable but does not repair the underlying damage. Full repair requires advanced tools that can rewrite the magnetic data on the platters.

When should I run CHKDSK?

Running CHKDSK on a regular basis can help detect emerging bad sectors before they multiply and cause major issues. It should especially be used if you notice potential signs of disk problems.

What tools can physically fix bad sectors?

Utilities like SpinRite, HDDSuperClone, HDD Regenerator, and others can interface with disks at a very low level to repair bad sectors by rewriting data. This is beyond the abilities of CHKDSK.

Table Comparing CHKDSK to Bad Sector Repair Tools

Utility Detection Ability Isolation Method Physical Repair Capability
CHKDSK Detects bad sectors Marks bad sectors as unusable No
SpinRite Detects bad sectors Rewrites data to bad sectors Yes
HDDSuperClone Detects bad sectors Remaps bad sectors Yes

This table summarizes the capabilities of CHKDSK versus more advanced repair tools. While CHKDSK can find bad sectors, it cannot truly fix them like SpinRite or HDDSuperClone which can operate at the disk level.


CHKDSK is built into Windows and available from the command line. To run it:

  1. Open the Command Prompt as administrator
  2. Type “chkdsk C: /f” and hit Enter to run it on C: drive
  3. Type “Y” and hit Enter to confirm you want to run it
  4. Let CHKDSK complete – this may take a while
  5. Restart computer when prompted

CHKDSK will output any errors found and mark bad sectors automatically. However, you need third-party tools like SpinRite to actually repair bad sectors that CHKDSK detects.

Hard Drive Repair Tools


SpinRite is a renowned hard drive recovery and maintenance tool available from It can:

  • Find and repair physical bad sectors
  • Recover data from damaged drives
  • Enhance drive performance
  • EXTENDS drives’ lifespan

SpinRite provides capabilities far beyond CHKDSK for bad sector repair and data recovery. It works at the physical disk level to maximize drives’ health.


HDDSuperClone is another advanced data recovery tool that repairs bad sectors. Key features include:

  • Bad sector remapping
  • Sector-by-sector disk cloning
  • S.M.A.R.T. drive health monitoring
  • Imaging drives for backup

HDDSuperClone provides an all-in-one solution for drive health checks, bad sector repairs, and full drive imaging for backups or clones.

HDD Regenerator

HDD Regenerator specifically targets bad sector repair. It:

  • Locates bad sectors
  • Repairs damaged areas
  • Writes repaired data patterns to stabilize sectors
  • Fills in magnetic voids with placeholders

For comprehensive bad sector repair, HDD Regenerator is a specialized tool worth considering beyond just using CHKDSK.