Reset FSX.cfg safely in boxed FSX or Steam Edition, find the active profile, force a clean rebuild and preserve essential add-on entries.
To reset FSX.cfg, close Microsoft Flight Simulator X, find the active fsx.cfg in your AppData profile, rename it to fsx.cfg.old, then start FSX again. FSX or FSX: Steam Edition will generate a fresh file using detected hardware defaults; keep the old file so you can restore essential add-on entries.
How do I rebuild FSX.cfg safely?
The safest method is to preserve the old configuration and let FSX create a replacement automatically.
- Close FSX completely. With Steam Edition, wait until the simulator process has stopped before changing any files. Otherwise, FSX may write the old configuration back when it exits.
- Open the configuration directory. Press Windows key+R, enter
%APPDATA%\Microsoftand press Enter. - Find the active profile. Open the
FSXorFSX-SEfolder, depending on your installation. If both exist, use the file whose modified time changes after you alter a harmless FSX setting and exit normally. - Back up the file. Copy
fsx.cfgsomewhere outside the profile folder. Then, with filename extensions visible in File Explorer, rename the original tofsx.cfg.old. - Start FSX. Allow the main screen to load, then exit normally once. FSX will create and save a fresh
fsx.cfg. - Reconfigure gradually. Set your display resolution, graphics options, sound, traffic and other preferences. Run a short test flight before restoring any manual tweaks.
Do not delete the entire FSX or FSX-SE profile folder. It can contain other files used by modules, controls and add-ons. Our safe FSX.cfg editing checklist covers backups and restoring individual entries without undoing the reset.
Which FSX.cfg folder should I use?
Use the profile containing the configuration file that FSX actually updates, rather than choosing solely by the simulator's edition name.
| Installation | Possible configuration folder | What to check |
|---|---|---|
| Boxed FSX | %APPDATA%\Microsoft\FSX | Normally the active boxed-edition profile |
| FSX: Steam Edition | %APPDATA%\Microsoft\FSX-SE | Common when Steam Edition has a separate profile |
| Steam-only or migrated installation | %APPDATA%\Microsoft\FSX | Some installations use this folder instead |
If both directories are present, compare the files' modified times after changing one setting and closing FSX. Our guide to locating the active FSX.cfg profile explains the edition and Windows folder differences in more detail.
What does resetting FSX.cfg change?
A rebuilt file resets only the settings and custom lines stored inside fsx.cfg; it is not a complete reinstall or reset of every FSX file.
- Many graphics, display, sound, realism and traffic values return to hardware-detected defaults.
- Hand-added performance tweaks and custom parameters are removed from the active configuration.
- Custom
SimObjectPathscan disappear, so aircraft or other objects stored outside the standard folders may stop appearing. - The
[Trusted]records are rebuilt, which can cause legitimate gauges or modules to request permission again. - Installed aircraft, scenery and missions are not deleted.
- Files such as
scenery.cfg,dll.xml,exe.xml, controller profiles and saved flights are separate and are not reset by replacing onlyfsx.cfg.
The Reset Defaults buttons inside FSX affect the settings shown on their particular pages. They do not reliably remove obsolete or manually inserted lines, which is why renaming fsx.cfg is the cleaner troubleshooting reset.
A mistake we see constantly is copying the whole old file back after FSX begins working. That restores the fault as well. Copy only entries an add-on genuinely requires, one group at a time, and let FSX rebuild trusted-module records itself.
What if FSX does not create a new FSX.cfg?
If no replacement appears, FSX is usually using another profile folder or cannot write to the selected directory.
- Check both
FSXandFSX-SEunder%APPDATA%\Microsoft, then compare modified times. - Confirm the simulator was fully closed before renaming the file and exited normally after the test launch.
- Check that the profile directory is writable and that the new file has not been marked read-only by another utility.
- Temporarily stop any add-on manager that automatically inserts or restores configuration entries, then repeat the rebuild.
Do not use ResetXDirectorySecurity.exe as a substitute for this procedure. It addresses installation-folder permissions rather than regenerating the configuration; our explanation of what ResetXDirectorySecurity.exe actually repairs clarifies when that utility is appropriate.
If FSX still crashes with a newly generated configuration, the fault probably lies elsewhere. Continue with the broader FSX crash checks for add-ons, modules and damaged files rather than repeatedly deleting the new configuration.