Your computer has slowed down or an unfamiliar pop-up keeps appearing. Those symptoms deserve attention, but they can also have causes other than malware. To check whether your PC has a virus, update your security software and run a scan; then use its findings to decide what to do next.
Check Computer for Malware With Windows Security
On a Windows 11 PC, open Windows Security from the Start menu and select Virus & threat protection. Under Protection updates, choose Check for updates to get the latest security intelligence. These updates help Microsoft Defender recognize known threats. If another antivirus is active, open that program and update it using its own controls.
Next, choose Quick scan. This checks locations where threats are commonly found and is a useful first step when you want to check a computer for malware. Let the scan finish and read the result rather than closing the window as soon as the progress bar disappears. If the app recommends another scan, follow that instruction.
A slow computer, browser redirects, or unexpected ads can be clues, but none identifies a virus by itself. For example, a browser extension can change your homepage, and a nearly full drive can slow a PC. A named detection in your security application’s results gives you a more specific issue to investigate.
Choose a Deeper Scan
If you are wondering how to check if my computer has a virus after opening a suspicious attachment or seeing repeated warnings, run a full scan. In Virus & threat protection, select Scan options, choose Full scan, and select Scan now. It examines files and programs more broadly than a quick scan and can take longer. Keep the computer powered on while it runs.
To check a computer for virus activity that may be difficult to detect while Windows is running, consider Microsoft Defender Antivirus (offline scan) in the same scan options. Save open work first: Windows restarts, scans in its recovery environment, and restarts again. Afterward, open Protection history in Windows Security to see the result. Microsoft’s scan guidance describes the available choices.
If the PC belongs to your employer or school, follow its IT instructions before changing security settings. Do not download an unfamiliar scanner from a pop-up claiming that your device is infected. Close the page and open your installed security application directly.
Read the Result and Respond
A detection may show a threat name, affected file, and action such as quarantine or removal. Open Protection history for details and follow the recommended action. Quarantine isolates a suspicious item; do not restore it merely because an application stops working. If you believe the detection is mistaken, investigate the file with the software provider or ask your IT team before allowing it.
When you ask how to check if my computer has a virus, the scan result is only one part of the answer. If the tool reports that it could not remove a threat, or alerts return after cleanup, disconnect the PC from the network and seek help from Microsoft Support or a qualified technician. From a separate trusted device, change important passwords if you suspect they were exposed.
If no threat is found, install pending system and browser updates and investigate the specific symptom, such as a new browser extension. A clean scan lowers suspicion but cannot rule out every threat. If the problem persists, run the recommended deeper scan or seek technical help; if a threat was removed, confirm the security app reports it handled and continue monitoring.