Steam disk write error when installing or updating a game

The error

The message appears in the Steam client when a download or update stops:

An error occurred while updating <game title> (disk write error)
An error occurred while installing <game title> (disk write error)

Steam Support explains that this "An error occurred while…" message means Steam could not complete the installation, and that the specific reason is shown in the parentheses at the end. Here the reason is "disk write error": the download reached your computer, but writing it to disk failed.

Why it happens

Steam Support's general install and update troubleshooting lists these causes on its Update & Installation Issues page:

• Library folder permissions. The Steam library folder holds every installed game, and Valve states that it "need[s] to be writable by all users in order to update properly". Those permissions sometimes break and need to be refreshed.
• Corrupted files on the drive. Files can become corrupted through bad hardware, software crashes or power surges, which stops Steam from patching them.
• Antivirus software. Valve notes that antivirus software "hooks very deep" into the system and can affect disk operations, and that some games' copy protection can trigger false-positive alerts.
• Other programs that monitor the disk. Anything that modifies or monitors disk activity, such as system cleaners, recording software or performance boosters, can interfere with a download.
• Errors on the drive itself. All storage can suffer file corruption, especially older drives or drives under heavy load.

Two Windows settings can also block writes. Controlled folder access in Windows Security blocks unapproved apps from changing files in protected folders, and a disk marked read-only accepts no writes at all. A drive with no free space cannot take new files either.

How to fix it

Work down the list and retry the download after each step.

1. Restart Steam, then the computer. Steam Support calls this the first step: a restart releases locks on files and other resources held by other programs.

2. Check free space on the library drive. Open File Explorer, select This PC, and read the free space under Devices and drives, as Microsoft describes. To make room, go to:

   Start > Settings > System > Storage > Cleanup recommendations
   

3. Clear the download cache. This makes Steam drop its locally cached configuration data and fetch it again from the Steam servers. Valve's path:

   Steam > Settings > Downloads > Clear Cache
   

4. Repair the library folder. This refreshes the folder permissions that let Steam write into it:

   Steam > Settings > Storage > ... > Repair Folder
   

   Pick the drive that holds the failing game, open the ... menu and choose Repair Folder.

5. Verify the game's files. Following Verify Integrity of Game Files:

   Library > right-click the game > Properties > Installed Files > Verify integrity of game files
   

   Steam checks every file and re-downloads the ones that are wrong. Valve warns against running it while you defragment or scan for viruses, and against verifying several games at once.

6. Clear the read-only attribute on the game's files. Use the attrib command, which Microsoft documents with -r to clear Read-only and /s to include subdirectories. Close Steam, open Command Prompt, and run it on the game's folder. With the default library path from Steam Support:

   attrib -r "C:\Program Files (x86)\Steam\steamapps\common\<game folder>\*.*" /s
   

   Replace <game folder> with the game's folder name, and the path with your own library if the game is on another drive.

7. Allow Steam through Controlled folder access. If Windows Security shows "App is blocked" when Steam writes, open Windows Security and go to:

   Virus & threat protection > Manage ransomware protection > Allow an app through Controlled folder access
   

   Choose Add an allowed app and browse to steam.exe.

8. Check other antivirus software. Valve's advice is to add exceptions for Steam in the antivirus, for example by excluding the Steam library folders from live monitoring, or to disable it briefly to test. Turn it back on once you have your answer.

9. Clear a read-only flag on the whole disk. This applies to a second or external drive that refuses every write. In an administrator Command Prompt, run diskpart, then:

   list disk
   select disk <number>
   attributes disk
   attributes disk clear readonly
   

   attributes disk on its own shows whether the disk is marked read-only; clear readonly removes that flag. Check the disk number against the size shown by list disk before you select it. The commands come from Microsoft's DiskPart reference.

10. Check the drive for errors. Valve's Windows path:

    This PC > right-click the drive > Properties > Tools > Error checking
    

11. Install to another library folder. Valve suggests testing on another drive. Add a library with:

    Steam > Settings > Storage > +
    

    Then install the game there, or select it in Storage and use Move, as described in Moving a Steam Installation and Games. If the download completes on the new drive, the old location is the problem.

12. Reinstall Steam to the same location. Download the installer from the Steam store and install over the existing copy. Valve says installing into the same location keeps your installed games, and warns that uninstalling Steam deletes all game content.

Check that it worked

Retry the update from the Downloads page or click Update on the game. The progress bar should run to the end without the "(disk write error)" message. Then verify the game's files once more: a clean pass, or a note that one or more files failed to verify, means the install is complete. Steam Support says those failures are local configuration files and can be ignored.

When the error only hits one drive or one folder

If every game on one drive fails but games on another install normally, the issue is that drive or its library folder, not your Steam account. Run Repair Folder on that library, check its free space, and look at the disk-level read-only flag and error checking (steps 9 and 10). A library you created inside Documents, Desktop or another folder that Controlled folder access protects can be blocked if Controlled folder access is turned on and Windows shows "App is blocked"; add Steam to the allowed list. Valve also advises against installing Steam itself to an external hard drive, because of possible performance issues.

If only one game fails, start with step 5, then step 6 on that game's folder.

If none of this helps

Steam Support recommends asking a local IT support specialist when the error survives these steps, because the remaining causes, such as antivirus behaviour, drive errors or memory errors, sit outside Steam. Valve's list also includes updating Windows and its drivers through Check for updates. Other guides on this site: a printer that Windows 11 shows as offline is covered in printer offline in Windows 11. For a game that installs but will not connect, see Roblox error code 279, Roblox's connection error. A streaming app showing an error code is covered in Disney+ error code 83.