How to Turn Smart App Control On/Off in Windows 11

Smart App Control Modes

Smart App Control has three states: On, Off, and evaluation mode. In evaluation mode (a trial period), Windows watches the apps you use without blocking anything. It then decides whether the feature suits how you work.

If it does, Windows turns Smart App Control on permanently. If it would cause too many interruptions, Windows turns it off.

Should I turn off Smart App Control? Leave it on if you mostly run mainstream, signed software, since it blocks untrusted apps for you. Turn it off if it keeps blocking an app you rely on and nothing else solves the problem.

To unblock an app from Smart App Control, know that Windows doesn’t let you allow a single app. You have two choices:

• Turn off Smart App Control completely. This lowers protection for every app, not only the one you want to run.
• Ask the app’s creator to digitally sign their software. A digital signature is a cryptographic stamp that confirms who made the software and that it hasn’t been changed since. Windows uses it to verify the app is safe.

Smart App Control may show as off, or may not let you turn it on, for these reasons:

• You turned it off earlier.
• Your device runs Windows in “S mode”. You would have to switch out of S mode and reset the PC.
• Optional diagnostic data is turned off in Windows.
• Your PC has the known issue described below.

If Smart App Control is off and your Windows version doesn’t let you switch it back on, you will likely need to reset or reinstall Windows. During setup, select “Send optional diagnostic data”. On version 26H2 and later, a clean installation is no longer required to turn the feature on or off.

The first thing to try if you can’t turn Smart App Control on is to install KB5127936, released October 27, 2026. Microsoft says it fixes an issue where Smart App Control could not be turned back on after it was turned off, with the option greyed out. Open Settings › Windows Update, select Check for updates, install what appears, and restart if Windows asks. Then check the option again.

Microsoft lists the underlying known issue in KB5127648. After you install that update, some devices might be unable to turn on Smart App Control if it was turned off, and the On option might be greyed out. Devices that already have Smart App Control on are not affected.

Microsoft resolved the issue in Windows 11 versions 26H2 and 25H2 with updates released on or after October 27, 2026 (KB5127936). If you can’t update yet, Microsoft says 24H2 users can apply a registry workaround, which the KB5127648 support article covers. Windows 11 24H2 Home and Pro reached end of updates on October 13, 2026, so moving to 25H2 or 26H2 is the better long-term fix.

How to Turn Smart App Control On or Off Using Windows Security

Windows Security is the main place to manage Smart App Control. From there you can check your protection status and change how apps are blocked. This is the safest method, so try it before the registry.

If the On option is greyed out, install KB5127936 through Settings › Windows Update before you start. On versions before 26H2, turning Smart App Control off can be permanent without a reset, so choose Off only when you are sure.

The steps below open Smart App Control settings, where you can disable Smart App Control in Windows 11 or turn it back on.

1. Open Windows Security. Search for “Windows Security” in the Start menu⊞, or click the shield icon near the clock in the taskbar🖥️ tray. You can also press Win+I to open Settings⚙️, then go to Privacy & security › Windows Security › Open Windows Security. The Windows Security window opens.
2. Select App & browser control in the left pane. The app and browser protection options appear on the right.
3. Select the Smart App Control settings link. A page with the Smart App Control options opens.
4. Select the option you want by clicking the circle next to it.

   • OnBlocks untrusted or harmful apps.
   • OffTurns off Smart App Control.
   • Evaluation modeWindows tests whether Smart App Control suits your system without blocking anything. This option is not always visible, usually because the PC is no longer in the evaluation period.

   If an option is greyed out or missing, the cause is usually one of the conditions listed earlier, such as S mode, diagnostic data being off, or the KB5127648 issue. On versions before 26H2, a greyed-out On option often means the feature was already turned off.
5. Select Yes if User Account Control asks for permission. Windows applies your choice. You can come back to this page at any time to check the current state or change it.

That’s it. You’ve changed your Smart App Control setting using Windows Security, and the page now shows the state you picked.

Manually Adjusting Smart App Control Using Registry Editor

The Registry Editor is the Windows tool that stores low-level settings, and you can use it to adjust Smart App Control. This is useful when the options in Windows Security are greyed out or missing, including after the KB5127648 issue on 24H2. Be careful: a wrong edit in the registry can make Windows unstable. If you’re not comfortable with this, use the Windows Security method instead.

Administrator rights are required for these steps. Before you change anything, create a backup. In Registry Editor, select File › Export, choose a location, and save the file. If something goes wrong, you can import it again with File › Import.

If S mode is the reason the option is unavailable, switch out of S mode first, as described earlier. The steps below turn Smart App Control on.

Turning Smart App Control ON

1. Open Registry Editor. Press Win+R, type regedit, and press Enter. Select Yes if User Account Control asks. Registry Editor opens.
2. Go to the Smart App Control registry key. Use the address bar at the top of Registry Editor to reach the key that controls Smart App Control, then set its value so the feature is on. When the standard menu options are greyed out, this is the way to force the feature active.
3. Restart your🔄 computer after closing Registry Editor. The change does not take effect until Windows restarts. After the restart, check the state in Windows Security › App & browser control › Smart App Control settings.

That’s it. Smart App Control is now set to on, and the Smart App Control settings page should show the new state after the restart.

The steps below put Smart App Control back into evaluation mode. Windows then tests your software environment again, without fully blocking unverified apps, to decide whether the feature suits how you use your PC.

Setting Smart App Control to Evaluation Mode

1. Open Registry Editor. Press Win+R, type regedit, and press Enter. Select Yes on the User Account Control prompt. Registry Editor opens.
2. Go to the same Smart App Control registry key. Change its value to the evaluation setting. This makes Windows re-evaluate your app usage.
3. Restart your🔄 PC after closing Registry Editor. Windows then begins a new evaluation period.

You should now have Smart App Control back in evaluation mode, with Windows watching your apps without blocking them.

The steps below turn Smart App Control off completely. Windows then stops blocking untrusted applications and unverified files. Use this route if the toggle in Windows Security is greyed out after your evaluation period ends.

Turning Smart App Control OFF

1. Open Registry Editor. Press Win+R, type regedit, and press Enter. Select Yes to approve the User Account Control prompt. Registry Editor opens.
2. Go to the same Smart App Control registry key. Change its value to the off setting.
3. Restart your🔄 computer after closing Registry Editor. Smart App Control stays off until you change the setting again.

That’s it. Smart App Control is now off, and Windows no longer blocks untrusted apps through this feature.

To undo any of these edits, repeat the steps with the value you want, or import the backup you exported earlier. If you’re unsure about using the Registry Editor, the Windows Security app is the safer choice.

Summary

If the On option stays greyed out, install KB5127936 first. Microsoft fixed the KB5127648 issue in 25H2 and 26H2 updates released on or after October 27, 2026. If your PC still runs 24H2, which no longer receives updates on Home and Pro, move to 25H2 or 26H2 or use the registry workaround from the KB5127648 article.

To undo a change, return to Smart App Control settings in Windows Security and pick the other option. On versions before 26H2, turning the feature back on may still need a reset or reinstall.