Best antivirus software for windows vista

If you must keep using Windows Vista, my pick would be Avast Free Antivirus 18. 8.

• Best practical choice: Avast Free Antivirus 18. 8. Avast says this is the final version compatible with Vista and that it still receives virus-definition updates, although it gets no program updates, bug fixes, or technical support. support.avast.com
• Important limitation: Windows Vista itself has been unsupported since April 11, 2017, so antivirus software cannot fully compensate for the operating system's unpatched security vulnerabilities. learn.microsoft.comsupport.microsoft.com
• Avoid downloading random "Vista antivirus" installers from third-party sites. If you use Avast, use Avast's official Vista page. Avast's official Windows Vista antivirus page

My recommendation

Avast 18.8 + very cautious browsing is probably the best combination if the Vista computer absolutely cannot be upgraded.

For a Vista PC that you use for banking, email, shopping, or other sensitive activities, though, I would strongly recommend upgrading the operating system or replacing the machine rather than relying on antivirus alone. Microsoft explicitly warns that unsupported Windows versions are at greater risk from malware because they no longer receive security fixes. learn.microsoft.comsupport.microsoft.com

If you tell me whether your Vista computer is 32-bit or 64-bit and how much RAM it has, I can also recommend the lightest antivirus/security setup for it.