Microsoft Defender Antivirus
The free, built-in option that now genuinely competes with paid suites on raw detection
Last updated September 22, 2026
Editor score
Pricing
Free
Included with Windows 10 and 11 — no download, signup or trial period required.
Independent lab results
- AV-TEST protection
- 6/6 protection — perfect score, February 2026 evaluation (12,000+ malware samples)
- AV-Comparatives
- 99.0% real-world protection, 0 false positives (2026 test round)
- False positives
- Lowest recorded false-positive rate of any product in the same AV-Comparatives table
AV-TEST Feb 2026; AV-Comparatives Real-World Protection Test, 2026
Pros
- +Costs nothing and requires no separate installation on Windows 10/11
- +Perfect AV-TEST protection score and the lowest false-positive rate in recent AV-Comparatives rounds
- +No subscription to manage, cancel, or get upsold on
- +Tightly integrated with Windows — no conflicts with OS updates or duplicate background scanning
Cons
- –Windows only — no Mac, Android or iOS protection
- –No VPN, password manager, backup, or identity monitoring — it is antivirus and nothing else
- –Full phishing/web protection depends on using Microsoft Edge; it's noticeably weaker in other browsers
- –Offline detection (no live cloud lookup) trails top paid suites
The most surprising trend in antivirus testing over the past few years isn’t a new challenger brand — it’s that the antivirus already sitting on every Windows PC has gotten genuinely good. Microsoft Defender scored a perfect 6/6 for protection in AV-TEST’s February 2026 evaluation, run against more than 12,000 malware samples, and posted a 0% false-positive rate in AV-Comparatives’ 2026 real-world test — the cleanest false-positive record in that comparison table, ahead of every paid competitor.
What it actually gets right
It’s free, it’s already installed, and it doesn’t nag you to upgrade every time it opens. For a large share of home users — people who keep their OS updated, don’t download cracked software, and mostly browse in Edge or Chrome with reasonable caution — Defender’s detection numbers now sit close enough to the paid leaders that paying for a third-party suite is a matter of wanting extra features, not needing better malware protection.
Where it falls short
Defender is Windows-only, full stop. If your household has a mix of Mac, Android and iOS devices, it covers none of them, and you’ll need something else regardless of how good it is on Windows. It’s also strictly antivirus: no VPN, no password manager, no dark web monitoring, no cloud backup. And its web-protection features lean heavily on Microsoft Edge — switch to Chrome or Firefox and some of that protection is noticeably thinner.
Independent testers also still note that offline detection (without a live connection to Microsoft’s cloud reputation service) trails the top paid suites, which matters mainly in edge cases like an infected USB drive on a machine with no internet.
Who should choose it
If you’re a Windows-only household who doesn’t need a VPN or identity monitoring bundled in, Defender is a legitimate answer to “what antivirus should I use” — not just a fallback. If you want cross-platform coverage or extra features, it’s worth comparing against Bitdefender or Norton 360 in our best free vs. paid antivirus guide.