New Fst — Dolphin Iosfs Failed To Write

A. Run Dolphin as Administrator
Right-click the Dolphin executable and select Run as administrator. This mitigates most permission-related failures.

B. Check Free Disk Space
Ensure the drive containing your ISOs and Dolphin’s cache folder has at least double the size of the game ISO free. For a 1.35 GB GameCube ISO, keep 3 GB free.

C. Disable Read-Only on the ISO
Right-click the ISO file > Properties > Uncheck Read-only > Apply.

When Dolphin rebuilds the FST and writes a new ISO, it often needs to create a temporary copy of the entire disc image. If your drive has less than 2–3 GB of free space (or the size of the game plus overhead), the write operation will fail.

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. dolphin iosfs failed to write new fst

The error message "IOS_FS: Failed to write new FST" in Dolphin Emulator typically indicates that

the software is unable to save or update the virtual file system metadata (the File Selection Table, or FST) on the emulated Wii NAND . This is most often a permissions issue

, where Dolphin lacks the necessary authorization to write to its own user directory. Common Causes Security Software Blocking Access

: Antivirus programs, particularly Windows Defender's "Controlled Folder Access" or Avast, often flag Dolphin’s frequent read/write operations as suspicious and block its ability to modify files in the Insufficient Permissions : If Dolphin is installed in a protected directory (like C:\Program Files ), it may lack write access unless specifically granted. File Read-Only Status

: The Dolphin installation directory or the user config folder may be set to "Read-only" in its system properties. Android Storage Restrictions

: On Android 11 and later, changes in how apps access storage can trigger this error, especially if game files or the NAND are stored on an SD card. Recommended Solutions Grant Folder Exclusions Have you solved this error using a different method

: Add the Dolphin executable and its user folder (usually found in Documents\Dolphin Emulator ) to your antivirus exclusion list. Adjust Windows Security : Navigate to Virus & threat protection Manage settings Manage Controlled folder access

and ensure Dolphin is allowed through, or turn off the feature temporarily. Run as Administrator : On Windows, right-click the Dolphin shortcut and select Run as administrator to bypass standard folder restrictions. Verify Folder Properties : Right-click your Dolphin folder, select Properties , and ensure the attribute is unchecked for the folder and all subfolders. Use a Portable Setup : Create a blank text file named portable.txt in the same folder as Dolphin.exe

. This forces Dolphin to store all user data in its local directory instead of the system's Documents folder, which can circumvent many permission issues.

For more technical details on NAND emulation, you can check the Dolphin Emulator Wiki or browse community solutions on the Dolphin Emulator Reddit setting antivirus exclusions for a specific program?

The error message "dolphin iosfs failed to write new fst" originates from the Dolphin Emulator, specifically when attempting to save or modify files on a virtual Wii NAND (the Wii's internal storage system).

Here is the complete text explaining the cause, the technical details, and the step-by-step solution to fix it. macOS:

A corrupted ISO or WBFS file can also trigger this error.

Windows:

macOS:

Linux: Run Dolphin from the terminal with sudo temporarily to test, but the better fix is:

chown -R $USER:$USER ~/.dolphin-emu/
chmod -R 755 ~/.dolphin-emu/

Below are the most effective solutions, ranging from quick checks to advanced workarounds.