SmartScreen Prevented Unrecognized App — Windows Defender SmartScreen Block

Fix Windows Defender SmartScreen blocking an application from starting with the 'Windows protected your PC' warning for unrecognized or unsigned programs. This guide covers everything you need to know about this topic, including common causes, step-by-step solutions, and answers to frequently asked questions.

Here are the key things to understand: SmartScreen checks downloaded executables against Microsoft's reputation database. Applications without a valid code signing certificate or without established reputation are flagged. The blue 'Windows protected your PC' screen prevents the application from running by default. SmartScreen also checks URLs in Edge and Microsoft Store apps for known malicious content. New legitimate software often gets flagged until it builds reputation through sufficient downloads. Understanding these fundamentals will help you diagnose and resolve this issue more effectively.

The most common reasons this occurs include: Application is not digitally signed with a code signing certificate. Application is newly released and has not built up reputation in Microsoft's database. Application downloaded from the internet has a Mark of the Web (MOTW) zone identifier. Software actually contains malware or potentially unwanted software (PUP). Identifying the root cause is the first step toward finding the right solution.

To resolve this, follow these recommended steps: Click 'More info' on the SmartScreen warning, then click 'Run anyway' if you trust the source. Right-click the downloaded file > Properties > check 'Unblock' at the bottom to remove MOTW. Scan the file with Windows Defender or VirusTotal.com before running unrecognized software. For developers: code sign your application with a trusted certificate to prevent SmartScreen warnings. For IT admins: configure SmartScreen via Group Policy rather than disabling it system-wide. If these steps do not resolve the issue, consider consulting additional resources or a qualified professional.

This article is part of our Windows Error Codes collection on Error Codes Wiki. We provide comprehensive, up-to-date information to help you find solutions quickly.