Microsoft Defender may block an app because it doesn't recognize it as safe
When you try to open an app and Microsoft Defender stops it, the program has flagged the file as potentially unsafe — either because it's brand new, unsigned, or because Defender's threat detection thinks it matches a known risk pattern. This doesn't always mean the app is actually dangerous. Defender errs on the side of caution, especially with programs it hasn't seen before or ones downloaded from the internet.
You have several ways to open the app anyway. The fastest is to tell Defender to allow it just this once. If you use the app regularly, you can add it to an exclusion list so Defender stops blocking it permanently. A third option is to temporarily turn Defender off, though this leaves your computer unprotected and is not recommended unless you're certain the app is safe.
Key Takeaways
- When Defender blocks an app, a notification appears with an "Allow" button — clicking it lets the app run without permanently changing your security settings.
- If you use the app often, add it to Defender's exclusion list through Settings so it stops blocking the file every time.
- You can exclude a specific file, a folder, a file type, or a process name, depending on how broadly you want Defender to stop checking.
- Turning Defender off entirely is possible but leaves your computer unprotected; only do this if you're certain the app is safe and you plan to turn it back on immediately after.
Allow the app to run one time through the notification
When Defender blocks an app, a notification usually appears on your screen. Look for a message that says "Threat detected" or "This app has been blocked for your protection." The notification includes an "Allow" button or "Allow on this device" option.
Click that button. Defender will let the app run this time without making any permanent changes to your security settings. The next time you open the same app, Defender may block it again unless you add it to an exclusion list.
If the notification disappears before you click it, or if no notification appears, the app may have been blocked before it could run at all. In that case, move to the next method.
Add the app to Defender's exclusion list permanently
If you plan to use the app regularly, adding it to Defender's exclusion list stops the blocking from happening every time. Open Windows Settings by pressing the Windows key and typing "Settings," then press Enter.
Go to Privacy & Security in the left sidebar, then select Virus & threat protection. Scroll down and click Manage settings under "Virus & threat protection settings."
Scroll down to Exclusions and click Add or remove exclusions. A new window opens. Click the plus sign (+) and choose what you want to exclude: File, Folder, File type, or Process.
If you choose File, browse to the app's .exe file on your computer and select it. If you choose Folder, select the entire folder where the app lives — this is useful if the app has multiple files Defender might block. If you choose File type, type the extension (like .exe or .bat) to exclude all files of that type. Click Add when done.
Find the app's location if you're not sure where it is
If you don't know where the app's files are stored, right-click the app's shortcut on your desktop or in your Start menu and select Open file location. This opens a folder showing the app's files.
If the app doesn't have a shortcut, open File Explorer and navigate to C:\Program Files or C:\Program Files (x86) — most installed apps live in one of these folders. Look for a folder with the app's name. If the app is in your Downloads folder or on an external drive, navigate there instead.
Once you find the app's main file (usually a .exe file with the app's name), you can add it to Defender's exclusion list using the method above.
Turn off Microsoft Defender temporarily if the app won't run any other way
Turning Defender off entirely is a last resort because it removes all real-time protection from your computer. Only do this if you're certain the app is safe and you plan to turn Defender back on immediately after.
Open Windows Settings, go to Privacy & Security, then Virus & threat protection. Under "Virus & threat protection settings," click Manage settings. Find Real-time protection and toggle it off. A warning appears asking you to confirm — click Yes.
Your computer is now unprotected. Open the app, use it, and then return to the same settings and toggle Real-time protection back on immediately. Do not leave Defender off for longer than necessary.
Check if the app itself is the problem, not Defender
Sometimes an app won't run even after Defender allows it. The issue might be that the app is outdated, missing a required file, or incompatible with your version of Windows.
Check the app's website or documentation to see if there's a newer version. If you downloaded the app from the internet, try downloading it again — the file may have been corrupted. If the app is very old, try running it in compatibility mode: right-click the app's .exe file, select Properties, go to the Compatibility tab, and check Run this program in compatibility mode for. Choose an older version of Windows from the dropdown and click Apply.
Frequently Asked Questions
Why does Defender block some apps but not others?
Defender blocks apps it doesn't recognize as safe, which often means apps that are new, unsigned by a publisher, or downloaded from the internet. Apps installed from the Microsoft Store or official publishers are usually recognized and allowed. Defender also blocks files that match patterns of known malware, even if the app itself is harmless.
If I add an app to exclusions, does that make my computer less safe?
Adding a specific app to exclusions means Defender stops scanning that one file or folder, but the rest of your computer remains protected. The risk depends on whether the app is actually safe. Only add apps you trust or have researched. If you're unsure whether an app is safe, search for its name plus "malware" or "virus" to see what others have reported.
Can I undo an exclusion if I change my mind?
Yes. Go back to Privacy & Security > Virus & threat protection > Manage settings > Exclusions, find the app or folder you added, and click the minus sign (-) next to it. Defender will start blocking that app again.
What if Defender blocks an app I downloaded but I'm not sure if it's safe?
Before allowing it, search the app's name on a search engine along with words like "safe," "malware," or "virus." Look at what reputable tech sites or security companies say about it. You can also upload the file to VirusTotal.com, a free service that scans files with multiple antivirus engines. If multiple engines flag it, the app is likely unsafe.