Extract and rebuild using GameCube ISO Tool or wit:
wit extract game.iso extracted/
wit copy extracted/ game_fixed.iso
Some AV software locks writes to emulator files.
Fix:
The "Dolphin iOSFS failed to write new FST" error is frustrating, but it is almost always fixable. In the vast majority of cases, the culprit is either a permissions issue or a corrupt FST file. Running Dolphin as an administrator (or fixing folder permissions) and deleting the old fst.bin resolves the problem instantly for most users.
If you are still stuck, consider backing up your saves and performing a clean reinstall of Dolphin. Remember to always dump your games legally from discs you own and enjoy the wonderful world of Wii and GameCube emulation without interruption.
Have you solved this error using a different method? Share your experience in the Dolphin community forums to help fellow emulation enthusiasts.
The error "IOS_FS: Failed to write new FST" in the Dolphin Emulator typically occurs when the program lacks the necessary permissions to write files to its user directory. This is often triggered by security software or restrictive folder settings that block the emulator from saving configuration data or temporary files. Common Fixes
Check Antivirus Settings: Security software like Windows Defender, Bitdefender, or Avast frequently blocks Dolphin's write attempts. You can try adding Dolphin.exe to your antivirus "allow" list or disabling features like "Controlled folder access" in the Windows Security center.
Run as Administrator: Right-click the Dolphin executable and select Run as administrator to bypass standard folder permission restrictions.
Move the User Folder: If your "Dolphin Emulator" folder is located in a synced directory like OneDrive, it may cause write conflicts. You can move it to a local, non-synced location or use a "portable.txt" file in the emulator's main folder to store settings locally.
Disable Read-Only Mode: Ensure the Dolphin installation and user directories are not set to read-only in their properties menu. Why this happens
The "FST" (File System Table) refers to the internal file structure of the Wii's operating system (IOS) that Dolphin emulates. When Dolphin starts or switches games, it attempts to update these temporary files in its user directory; if it cannot write the file, the emulator may fail to launch or crash during gameplay.
The error "IOS_FS: Failed to write new FST" in Dolphin Emulator typically occurs when the emulator is unable to modify its own configuration or Wii system files. This is most often a permissions issue rather than a software bug. Common Causes
Antivirus Interference: Many antivirus programs, including Windows Defender, block Dolphin from making changes to the fst.bin file because they perceive constant read/write actions as suspicious.
Restricted Folder Permissions: If Dolphin is installed in a system-protected folder like C:\Program Files\, it may lack the necessary "Full Control" to write data. dolphin iosfs failed to write new fst
Read-Only Attributes: The user directory (often in Documents/Dolphin Emulator) or the installation folder might be set to "Read-Only".
Updating Errors: Occasional issues during an auto-update can leave temporary files that block the creation of new ones. Step-by-Step Solutions 1. Grant Administrative Privileges
Running Dolphin as an administrator can bypass most permission blocks. Right-click the Dolphin.exe file and select "Run as administrator". 2. Add Antivirus Exclusions Your security software might be locking the fst.bin file. Open Windows Security > Virus & threat protection.
Select "Manage settings" and then "Add or remove exclusions".
Add the Dolphin installation folder and the user data folder (usually Documents\Dolphin Emulator) to the exclusion list.
Ensure "Controlled Folder Access" is turned off if it is blocking the app. 3. Change Installation Location
Avoid installing Dolphin in system-protected directories. It is recommended to create a dedicated folder like C:\Dolphin\.
Tip: You can make Dolphin "Portable" by creating a blank text file named portable.txt in the same folder as the emulator's .exe. This forces Dolphin to store all user data inside that folder instead of Documents. 4. Clear Temporary Files
Sometimes a file named fst.bin.xxx (a temporary file) is stuck and preventing the real fst.bin from being updated. Navigate to your user directory: Dolphin Emulator/Wii/. Locate and delete any files ending in .xxx.
Check if fst.bin is set to "Read-Only" in its file properties and uncheck it if necessary. 5. Repair the User Config Path (Windows Registry)
If you recently updated Dolphin and the error persists, the registry might be pointing to a dead path.
Navigate to HKEY_CURRENT_USER\Software\Dolphin Emulator in the Registry Editor.
Check the UserConfigPath value and ensure it correctly points to your actual Dolphin folder. Extract and rebuild using GameCube ISO Tool or
"IOS_FS: Failed to write new FST" in the Dolphin Emulator typically indicates that
the emulator is unable to save or modify files in its designated user folder
. This usually occurs because of insufficient file permissions, interference from security software, or issues with the location of the Wii NAND folder. Common Causes Antivirus Interference
: Programs like Windows Defender or Avast may block Dolphin's frequent read/write actions, incorrectly flagging them as suspicious behavior. Permission Issues : The Dolphin directory or the user data folder (usually in Documents/Dolphin Emulator
) may be set to "Read-only," preventing the creation of new FST (File System Table) files. NAND Path Configuration
: If the path to the Wii NAND is incorrect or points to a protected system directory, the emulator will fail to update its internal file structure. Android Storage Changes
: On Android 11 and later, scoped storage restrictions can prevent the app from writing to certain directories, especially if games are stored on an SD card. Recommended Solutions Run as Administrator Right-click the Dolphin executable and select Run as administrator . This often bypasses basic permission blocks on Windows. Add Antivirus Exclusions Go to your antivirus settings (e.g., Windows Security Virus & threat protection settings ) and add the Dolphin installation folder and the Documents/Dolphin Emulator folder to the Exclusions Check Folder Permissions Right-click your Dolphin Emulator folder (usually in Documents). Properties and ensure the box is unchecked. tab, ensure your user account has Full control Relocate or Reset User Data (Advanced) Wii NAND Fix
: Try changing the NAND path in Dolphin’s settings to a different, non-system folder. Folder Rename : Some users resolve the issue by renaming the Dolphin Emulator folder in Documents to just : This will reset your settings and save states. Wii Menu Cleanup
: For issues specifically involving the Wii Menu, navigate to Wii > shared2 > sys within your user folder and delete the folder while emulation is stopped. Android-Specific Fix
If you are on Android, ensure Dolphin has "All files access" permission in system settings. If games are on an SD card, try moving them to internal storage to see if the write error persists. Are you seeing this error when launching a specific game or when attempting a system update
The error message "IOS_FS: Failed to write new FST" in the Dolphin Emulator typically indicates that the emulator is unable to access or write to its required user configuration folder. This is usually caused by restrictive security settings or incorrect file pathing. Common Solutions
Disable Controlled Folder Access: Windows Security often blocks applications from writing to the "Documents" folder.
Go to Windows Settings > Update & Security > Windows Security. Select Virus & threat protection > Manage settings. Some AV software locks writes to emulator files
Scroll to Controlled folder access and turn it Off, or add Dolphin as an allowed app.
Whitelist in Antivirus: Third-party software like Avast or Windows Defender may flag Dolphin's frequent read/write actions as suspicious. Ensure the Dolphin executable and its "Dolphin Emulator" folder are added to your antivirus exclusion list.
Relocate the User Folder: If the error persists, move the user data out of the Documents folder. Open Dolphin and select File > Open User Folder.
Close Dolphin and move that "Dolphin Emulator" folder to a new location, such as your desktop or a non-system drive.
Alternatively, create a blank text file named portable.txt in the same folder as the Dolphin executable to force it to use its own directory for data.
Check Folder Permissions: Right-click your "Dolphin Emulator" folder (usually in Documents), select Properties, and ensure Read-only is unchecked for the folder and all its contents.
Registry Correction (Advanced): If Dolphin is looking for a directory that no longer exists, you may need to manually update the UserConfigPath registry key under HKEY_CURRENT_USER\Software\Dolphin Emulator.
For further troubleshooting, community discussions on Reddit and the Dolphin Forums offer detailed step-by-step guides for specific operating systems.
Did these steps clear the error for you, or are you still unable to boot games?
Dolphin may not have write access to the folder where the ISO or its temporary files are stored. This is especially common if:
Dolphin’s built-in filesystem editor is convenient but sometimes unreliable. Instead, use dedicated tools:
Basic workflow with GCReEx:
A corrupted ISO or WBFS file can also trigger this error.
Some GameCube ISOs are marked as read-only by the operating system. Additionally, if the ISO was ripped from a disc with unreadable sectors, the FST section might be corrupt to begin with.