Go to > Update & Security > Windows Security . Select Virus & threat protection .
The error "IOS_FS: Failed to write new FST" (or the similar "Failed to rename temporary FST file") signifies that Dolphin cannot modify files in its designated User directory. This is common after an update if the emulator's folder permissions change or if security software flags the frequent read/write activity as suspicious. Step-by-Step Solutions 1. Adjust Windows Defender Settings dolphin iosfs failed to write new fst
The most common cause is Windows Defender's , which prevents unauthorized apps from writing to the "Documents" folder where Dolphin typically stores data. Go to > Update & Security > Windows Security
If your "Documents" folder is restricted or synced with OneDrive, moving the data can stop the error. dolphin iosfs failed to write new fst