A: Some do (Avast was fined for selling user browsing data in the past). Microsoft Defender and Bitdefender Free have better privacy policies. Read the privacy statement before installing.

A: Bitdefender Free and Microsoft Defender are the lightest. Kaspersky Free is also light. Avast/AVG can be heavier.

Windows 11 is the most secure Windows version yet, but "secure" doesn't mean "invincible." While Microsoft Defender is built-in and excellent, many users still look for third‑party free antivirus software for extra layers of protection, a different interface, or features like a VPN, password manager, or PC cleaner.