Solve SmartScreen blocks, antivirus conflicts, error 1603 and permission problems on Windows 11.
If Windows shows "Windows protected your PC," click More info → Run anyway. This generic warning appears for new installers and does not mean the file is unsafe — Malwarebytes is digitally signed.
Right-click MBSetup.exe and choose Run as administrator. Missing admin rights is one of the most common reasons setup silently fails on Windows 11.
Temporarily pause any third-party antivirus that may be blocking the installer, then run setup again. Re-enable it afterwards. You do not need to remove Windows Defender.
Ensure at least 2 GB of free space. A partial or corrupted download also causes failures — download a fresh MBSetup.exe from malwarebytes.com and try again.
If you see error 1603 or setup fails from leftover files, run the free Malwarebytes Support Tool, choose Clean for a full removal, reboot, then install a fresh copy.
A pending Windows 11 update can block new installs. Open Settings → Windows Update, install everything pending, reboot, then run the Malwarebytes installer.
The most common causes are Windows SmartScreen blocking the installer, an existing antivirus conflicting with setup, insufficient disk space, a corrupted MBSetup download, or missing administrator rights. Running a fresh installer as Administrator resolves most cases.
Error 1603 is a fatal Windows Installer error, usually from leftover files of a previous version. Run the free Malwarebytes Support Tool, choose Clean for a full removal, reboot, then install a fresh copy of MBSetup.exe.
No. Malwarebytes is designed to run alongside Windows Defender and most antivirus products. You only need to temporarily pause a third-party antivirus during installation if it actively blocks the installer, then re-enable it afterwards.