How do I exclude a flight sim folder from Windows Defender?

To exclude a flight simulator folder from Microsoft Defender, open Windows Security, select Virus & threat protection, open Manage settings, then choose Exclusions and Add or remove exclusions. Select Add an exclusion > Folder, choose only the required simulator or add-on folder, and approve the administrator prompt.

Microsoft Defender Antivirus is still commonly called Windows Defender. These steps apply to Windows PC installations of Microsoft Flight Simulator, FSX, X-Plane, Prepar3D, DCS and other simulators, although the wording may differ slightly between Windows builds.

How do I add the folder exclusion in Windows 11 or 10?

You add a folder exclusion through the Virus & threat protection settings in Windows Security.

1. Open Windows Security: search for it from the Start menu and open the Windows Security application. Do not select Windows Defender Firewall.
2. Open the antivirus settings: select Virus & threat protection, then find the Virus & threat protection settings section and choose Manage settings.
3. Find Exclusions: scroll to Exclusions and select Add or remove exclusions.
4. Add the folder: choose Add an exclusion, select Folder, and browse to the required simulator, content or add-on directory.
5. Confirm the path: approve the administrator prompt and check that the complete folder path now appears in the exclusion list.

The exclusion normally takes effect immediately, so Windows does not usually need restarting. A folder exclusion also covers its files and subfolders, and it remains active until you remove it.

Which flight simulator folder should I exclude?

Exclude the narrowest folder that contains the files responsible for the verified scanning problem.

• If one trusted add-on triggers a false positive, exclude that add-on's own folder rather than the entire add-on library.
• If Defender repeatedly scans thousands of simulator content files during loading or an update, the simulator's package or content directory may be the relevant folder.
• If the issue concerns a development tool, exclude its output folder rather than the whole simulator installation.

A common mistake with Microsoft Flight Simulator is selecting the launcher or executable directory when the large content packages are stored elsewhere. Our guide to finding the actual MSFS installation and content paths explains the different locations.

Microsoft Flight Simulator 2020 and 2024 can also place the Community and Official directories in different locations depending on the chosen Packages path and storefront. Use the instructions for locating MSFS aircraft and package folders before creating the exclusion. Do not take ownership of the protected WindowsApps directory merely to reach an executable.

An exclusion is not a general frame-rate tweak. Consider one only when Defender's Antimalware Service Executable shows repeatable activity while the simulator reads or updates that folder. It will not fix a GPU bottleneck, insufficient memory, shader compilation or an overloaded aircraft system simulation.

Why is the Defender exclusion not working?

An exclusion usually appears ineffective because the wrong path was selected, the file was already quarantined, or another security feature is causing the block.

• The file was quarantined first: adding an exclusion does not restore a file that Defender has already removed. Check Protection history and restore or reinstall the file only after confirming that it came from a trusted source. If an MSFS add-on remains missing, follow our checks for an MSFS Community folder that is not loading add-ons.
• The wrong folder was excluded: confirm the complete path, especially when the simulator stores its launcher and content separately or an add-on manager uses an external library.
• Another antivirus is active: a Defender exclusion does not configure third-party security software. Add the narrow exception in the antivirus product that is actually providing real-time protection.
• The setting is managed: a greyed-out or missing Exclusions control usually means the account lacks administrator rights or the PC is controlled by an organisation's security policy.
• The block is not an antivirus scan: Controlled folder access, SmartScreen and file-system permissions are separate controls. A normal Defender exclusion does not grant write access or cure every access-denied message. For MSFS, use our checks for antivirus, folder protection and error 0x80070005.

Is excluding a simulator folder safe?

A narrow, temporary exclusion can be reasonable for a trusted simulator folder, but a broad permanent exclusion creates a genuine security risk.

Never exclude an entire drive, your whole user profile, the complete AppData tree or the Downloads folder. Anything copied into an excluded directory can avoid normal Defender Antivirus scanning. Scan downloaded archives before extracting or moving them into that directory, and treat add-ons containing executable files or DLL modules with particular care.

Use a folder exclusion rather than a process exclusion unless there is a specific, trusted reason to do otherwise. Excluding a process is not simply a way to exclude its EXE; it can also affect real-time scanning of files opened by that process.

How do I remove the exclusion?

Remove it from the same Exclusions list once the update, false-positive investigation or performance test is complete. Open Add or remove exclusions, select the listed path and choose Remove; Defender will resume scanning that folder and its contents.