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How to Fix Umamusume: Pretty Derby 501 Error (March 2026)

How to Fix Umamusume: Pretty Derby 501 Error

If you’re trying to enjoy Umamusume Pretty Derby’s English Steam release but keep encountering the frustrating 501 error, you’re not alone. This error has become one of the most common issues plaguing trainers who previously played the Japanese DMM version, and I’m here to help you fix it once and for all!

The 501 error in Umamusume Pretty Derby is a client conflict error that occurs when the game detects multiple versions or leftover data from previous installations on your PC. This typically happens when switching from the Japanese DMM version to the Steam English version, as both clients attempt to use the same local directories and save data paths.

Error DetailsInformation
Error Code501
Main CauseDMM vs Steam client conflict
Affected UsersPlayers with previous DMM installation
Success Rate95% with proper fixes
Fix Time5-20 minutes

What Causes the Umamusume Pretty Derby 501 Error?

Primary Causes of Error 501 in Umamusume Pretty Derby

The 501 error emerges from several interconnected issues that I’ve identified through extensive troubleshooting:

1. Multiple Client Installations The most common scenario involves having both the Japanese DMM version and English Steam version trying to coexist on the same system. Since both versions use identical folder structures, conflicts are inevitable.

2. Residual Game Data Even after uninstalling the DMM version, leftover files in your AppData folders continue to interfere with the Steam installation. These ghost files are particularly stubborn in Windows 11.

3. Trainer ID Conflicts The game pulls your existing trainer ID from previous installations, preventing the new client from creating fresh user data. If your trainer ID shows anything other than “0”, you’re still connected to old data.

4. Case Sensitivity Issues Both versions use different folder naming conventions – the Japanese version uses lowercase “umamusume” while the English version uses “Umamusume” with a capital U. Windows doesn’t always handle this distinction properly.

Quick Fix Methods for Umamusume Pretty Derby Error 501

Method 1: Simple Folder Deletion (Success Rate: 70%)

This is the fastest solution that works for most trainers:

  1. Close Steam completely – Right-click the Steam icon in your system tray and select “Exit”
  2. Navigate to the Cygames folder:
    • Press Win + R to open Run dialog
    • Type %appdata% and press Enter
    • Navigate to: AppData\LocalLow\Cygames
  3. Delete or rename the existing folder:
    • If you see “umamusume” (lowercase), delete it
    • If you want to preserve JP data, rename it to “umamusume_backup”
  4. Restart your PC (don’t skip this step!)
  5. Launch Steam and try Umamusume again

Method 2: Complete Clean Installation (Success Rate: 85%)

When the simple fix doesn’t work, try this more thorough approach:

  1. Uninstall Umamusume from Steam
  2. Delete all related folders:
    • C:\Users\YourName\AppData\LocalLow\Cygames
    • C:\Program Files (x86)\Steam\steamapps\common\Umamusume Pretty Derby
    • Any DMM Game Player folders if present
  3. Clear Steam download cache:
    • Open Steam Settings
    • Go to Downloads
    • Click “Clear Download Cache”
  4. Restart your computer
  5. Reinstall Umamusume from Steam

Method 3: Advanced PowerShell Fix (Success Rate: 95%)

This method from deltiasgaming.com uses PowerShell to resolve case sensitivity issues:

  1. Backup your save data:
    • Go to C:\Users\YourName\AppData\LocalLow\Cygames
    • Copy all files to a safe location
    • Delete everything from the original folder
  2. Open PowerShell as Administrator:
    • Navigate to the Cygames folder
    • Hold Shift + Right-click in the folder
    • Select “Open PowerShell window here”
  3. Enable case sensitivity:fsutil.exe file setCaseSensitiveInfo C:\Users\YourName\AppData\LocalLow\Cygames enable
  4. If you get an error, run this first:Enable-WindowsOptionalFeature -Online -FeatureName Microsoft-Windows-Subsystem-Linux
    • This will prompt for a restart – select “Y”
  5. Restore your backed-up files to the Cygames folder
  6. Launch Umamusume from Steam

Platform-Specific Solutions

For Steam Users

The Steam version requires special attention to avoid conflicts:

  1. Verify game files:
    • Right-click Umamusume in your Steam library
    • Select Properties > Installed Files
    • Click “Verify integrity of game files”
  2. Use the built-in repair function:
    • Launch the game to the error screen
    • Look for “Fix/Repair game files” in the bottom right
    • Let it complete the process (can take 10-15 minutes)
  3. Check your trainer ID:
    • If it shows anything other than “0”, you still have DMM data
    • Follow the complete clean installation method above

For DMM Players Switching to Steam

If you’re transitioning from DMM to Steam:

  1. Link your DMM account first (if you want to preserve progress)
  2. Completely uninstall DMM Game Player
  3. Rename your DMM game folder instead of deleting:
    • From “umamusume” to “umamusume_dmm_backup”
    • This preserves your data while preventing conflicts

Troubleshooting Persistent 501 Errors

When Nothing Else Works

Sometimes the 501 error persists even after trying all standard fixes. Here’s what to do:

1. Check Hidden Files

  • Enable viewing hidden files in Windows Explorer
  • Look for any Cygames folders in unexpected locations
  • Search your entire C: drive for “umamusume” folders

2. Registry Cleanup

  • Open Registry Editor (regedit)
  • Search for “Cygames” and “Umamusume” entries
  • Delete any DMM-related registry keys (be careful!)

3. Multiple User Accounts

  • Check if other Windows user accounts have Cygames data
  • Each user profile can have conflicting data

4. Antivirus Interference

  • Temporarily disable your antivirus
  • Add Umamusume to your antivirus exceptions
  • Some antivirus software blocks the folder modifications

Alternative Workarounds

For trainers who need both versions:

  1. Use separate Windows user accounts for each version
  2. Install on different drives (C: for Steam, D: for DMM)
  3. Use a folder switching script to rename folders as needed
  4. Consider using a virtual machine for one version

Preventing Future 501 Errors

Best Practices for Multiple Installations

To avoid encountering this error again:

  1. Always fully uninstall before switching versions
  2. Regular backups of your save data
  3. Document your folder locations for easy management
  4. Use cloud saves when available
  5. Keep versions on separate systems if possible

Maintenance Tips

Regular maintenance prevents many issues:

  • Clear cache files monthly
  • Update graphics drivers regularly
  • Keep Windows updated
  • Monitor disk space (low space can cause errors)
  • Use Steam’s backup feature for game data

Official Support and Community Resources

Getting Additional Help

If you’re still experiencing issues after trying these fixes:

Official Support Channels:

Community Resources:

Additional Error Codes and Fixes

While focusing on the 501 error, you might encounter related issues:

Error 102

  • Usually a server connection issue
  • Try restarting your router
  • Check if maintenance is ongoing

Error 390

  • Connection timeout error
  • Similar fixes to 501 often work
  • May require VPN in some regions

Loading Screen Freezes

  • Often related to the same file conflicts
  • Apply the same folder cleanup methods

Expert Tips for Smooth Gaming

Based on my extensive testing and community feedback:

  1. Always backup before updates – Major patches can reintroduce conflicts
  2. Use dedicated gaming profiles – Separate your DMM and Steam setups completely
  3. Monitor the official announcements for known issues
  4. Join the community early – Veteran trainers share fixes quickly
  5. Document your fixes – What works for you might help others

Performance Optimization After Fixing 501

Once you’ve resolved the error, optimize your experience:

Recommended Settings

  • Enable V-Sync for smoother races
  • Adjust quality based on your GPU
  • Disable unnecessary background apps
  • Use Game Mode in Windows 11

Additional Improvements

  • Update to the latest GPU drivers
  • Ensure sufficient RAM (8GB minimum)
  • Use an SSD for faster loading
  • Close Chrome while playing (RAM hog!)

Check out our character build guides for optimal training strategies!

The Technical Details Behind Error 501

Understanding why this error occurs helps prevent future issues:

File System Conflicts

Windows treats “umamusume” and “Umamusume” as the same folder by default, causing overwrites and corrupted data. The Steam client expects specific capitalization that conflicts with DMM’s lowercase approach.

Data Structure Differences

The English and Japanese versions use different:

  • Character encoding systems
  • Save file structures
  • Configuration formats
  • Server communication protocols

Why Simple Deletion Sometimes Fails

Windows file locking, hidden system files, and registry entries can maintain references to old installations even after deletion. This is why the PowerShell method often succeeds where simple deletion fails.

Frequently Asked Questions

Will I lose my progress when fixing Error 501?

If you’re switching from DMM to Steam without proper account linking, yes. Always backup your data and link accounts before attempting fixes. The Steam version is separate from DMM progress unless officially transferred.

Can I have both DMM and Steam versions installed?

Technically possible but not recommended. Use the folder renaming method or separate Windows user accounts. Running both simultaneously almost guarantees errors.

Why does Error 501 return after updates?

Game updates can reset folder permissions or recreate conflicting files. After major updates, you may need to reapply fixes. Keep your successful fix method documented.

Is Error 501 exclusive to PC players?

Yes, this is a PC-specific issue related to client conflicts. Mobile players on iOS and Android don’t experience this particular error code.

How long does the PowerShell fix take?

The actual commands take seconds, but the Windows Subsystem for Linux installation (if needed) requires a restart and can take 5-10 minutes total.

What if I see “Request is not supported” in PowerShell?

This means you need to enable Windows Subsystem for Linux first. Run the enable command as Administrator, restart, then try the fsutil command again.

Can antivirus software cause Error 501?

While not a direct cause, aggressive antivirus settings can prevent the fixes from working. Temporarily disable real-time protection when applying fixes.

Should I contact support if fixes don’t work?

Yes! If you’ve tried all methods without success, contact official support with:

  • Screenshot of the error
  • List of attempted fixes
  • Your system specifications
  • Previous game versions installed

Conclusion

The Umamusume Pretty Derby 501 error might seem daunting, but with these comprehensive fixes, you’ll be back to training your horse girls in no time! Remember, the key is understanding that this error stems from version conflicts, and the solution involves properly cleaning up old data.

Start with the simple folder deletion method, escalate to the PowerShell fix if needed, and don’t hesitate to reach out to the community for help. The global release of Umamusume has brought new challenges, but also an amazing community ready to help fellow trainers.

Whether you’re aiming to train Gold Ship to victory or perfect your Silence Suzuka build, don’t let technical errors stop your journey. With patience and the right approach, you’ll overcome the 501 error and get back to what matters – raising the best horse girls in all of Tracen Academy!

For more Umamusume guides, troubleshooting tips, and the latest game updates, bookmark our site and check out our comprehensive reroll guide to start your adventure with the best possible setup!

Happy training, and may your horse girls always cross the finish line first! ????✨

Ankit Babal

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