What is the best free antivirus?
Microsoft Defender is the best free antivirus for most people: top-tier protection, already installed, zero upsells. Avast One Essential is the best free suite on top of it (VPN allowance included), with AVG and Avira as solid alternatives.
The free champion is the one you already have. Microsoft Defender scores with the best in independent tests, integrates with Windows ransomware folder protection and SmartScreen, and is the only free option that never tries to sell you anything mid-scan. Turn on automatic updates and controlled folder access, and the baseline is genuinely strong.
Want more than the baseline without paying? Avast One Essential adds a real suite shell: the same engine as paid Avast, basic privacy tools, and 5 GB of VPN per week, the most generous free package going. AVG Free (same parent company, same engine) and Avira Free (with its handy software updater) are fine substitutes. All three will pitch upgrades; that is the price of free.
Who should not stay free: anyone managing a family's devices, running a business from their PC, or wanting phishing protection at full strength. That is where the $40-to-50 first-year suites earn their keep. And one warning stands regardless: "free antivirus" from a popup or cold call is malware with a logo.