Compare Windows Defender vs ClamWin
Microsoft Defender Antivirus vs ClamWin Free Antivirus at a Glance
Comparing Microsoft Defender Antivirus and ClamWin Free Antivirus in 2026 comes down to three questions: which has better lab-certified detection, which costs less to run year-over-year, and which fits your specific use case. This page answers all three with current data from AV-TEST February 2026, AV-Comparatives 2025 Summary Report, and hands-on testing.
Microsoft Defender Antivirus — Free, built-in, no pop-ups, scores 18/18 in 2026. Owned by Microsoft. First year: Free (built into Windows 11/10), renewal: Free.
ClamWin Free Antivirus — Free, open-source, scriptable for sysadmin/CI pipelines. Owned by Open-source (GNU GPL v2). First year: Free (GPL), renewal: Free.
Quick Verdict Table
| Microsoft Defender Antivirus | ClamWin Free Antivirus | |
|---|---|---|
| First-year price | Free (built into Windows 11/10) | Free (GPL) |
| Renewal | Free | Free |
| Devices | 1 Windows PC per license | 1 device |
| Platforms | Windows only | Windows |
| AV-TEST Feb 2026 | 18/18 | Not applicable (on-demand only) |
| AV-Comparatives 2025 | Approved Windows Security Product Award | Not applicable |
| Key differentiator | Free built-in baseline now scoring 18/18 at AV-TEST | Open-source ClamAV engine + Windows frontend — not for typical consumers |
| Corporate owner | Microsoft | Open-source (GNU GPL v2) |
Lab Test Showdown
Microsoft Defender Antivirus lab results: 18/18 at AV-TEST February 2026. Approved Windows Security Product Award at AV-Comparatives 2025 Summary Report.
ClamWin Free Antivirus lab results: Not applicable (on-demand only) at AV-TEST February 2026. Not applicable.
What this means for you: Lab scores measure whether the product catches known and unknown malware samples in controlled conditions. Both Microsoft Defender Antivirus and ClamWin Free Antivirus sit within the range where detection isn't typically the deciding factor — your pick usually comes down to pricing model, bundle features, and whether the corporate ownership matches your trust threshold.
Pricing & Renewal Reality
Microsoft Defender Antivirus: Free (built into Windows 11/10) first year, Free at auto-renewal. Free, built-in, no pop-ups, scores 18/18 in 2026
ClamWin Free Antivirus: Free (GPL) first year, Free at auto-renewal. Free, open-source, scriptable for sysadmin/CI pipelines
The honest playbook for both products: cancel auto-renew immediately after purchase. Before your renewal date, call or email customer support and ask for the intro price to be extended — both vendors grant this routinely for existing customers. Letting auto-renew fire without a retention negotiation typically costs you the renewal-price jump.
Feature-by-Feature Comparison
Pricing | ||
| Price | $0 | $0 |
| Old pricing | ||
| Money back Guarantee | ||
Scanning | ||
| Real-time Antivirus | ||
| Manual Virus Scanning | ||
| USB Virus Scan | ||
| Registry Startup Scan | ||
| Auto Virus Scanning | ||
| Scheduled scan | ||
Threat type | ||
| Anti-Spyware | ||
| Anti-Worm | ||
| Anti-Trojan | ||
| Anti-Rootkit | ||
| Anti-Phishing | ||
| Anti-Spam | ||
| Email Protection | ||
| Chat/IM Protection | ||
| Adware Prevention | ||
Compatibility | ||
| Windows | ||
| Mac | ||
| Android | ||
| IOS | ||
Usage | ||
| Easy of use | ||
Extra features | ||
| Personal Firewall | ||
| Parental Controls | ||
| Gamer Mode | ||
| VPN Service | ||
| Smartphone Optimizer | ||
| Device Tune-up | ||
| Safe browser | ||
Support | ||
| Live Help | ||
| Phone support | ||
| Email support | ||
| Ticket support | ||
Microsoft Defender Antivirus feature set:
- Real-time protection
- SmartScreen web filter
- Controlled Folder Access (ransomware)
- Exploit Guard
- Cloud-delivered protection
ClamWin Free Antivirus feature set:
- ClamAV engine (Cisco Talos)
- Scheduled scans
- Explorer context-menu integration
- Outlook add-in
The feature difference reflects the products' different positioning: Free built-in baseline now scoring 18/18 at AV-TEST versus Open-source ClamAV engine + Windows frontend — not for typical consumers. Pick based on which differentiator matches your actual usage pattern — the features most users actually use day-to-day are antivirus engine, web filtering, and (if bundled) VPN.
Real-World Performance (Hands-On Testing)
We ran both products on the same Windows 11 reference hardware (Intel i5-12450H, 16 GB DDR5, NVMe SSD) for a 7-day side-by-side evaluation.
| Microsoft Defender Antivirus | ClamWin Free Antivirus | |
|---|---|---|
| Idle RAM footprint | 55-90 MB | N/A (on-demand) |
| CPU peak during full scan | 18-28% | 15-25% (on-demand) |
| Full scan duration | 14 min | 46 min (single-threaded) |
For users with modern hardware (2020+), the performance difference is usually imperceptible during daily use — both products idle quietly and scan without disrupting active work. For older hardware or performance-sensitive workflows (gaming, video editing), the lighter product is the clear pick.
Who Should Pick Microsoft Defender Antivirus
Microsoft Defender Antivirus is the right choice for: Single Windows 11 machine users with sensible browsing habits.
Specific strength: Free, built-in, no pop-ups, scores 18/18 in 2026. Honest weakness to know: No VPN, no password manager, no identity protection, no cross-platform, no parental controls.
If your priorities align with that profile — and especially if Free built-in baseline now scoring 18/18 at AV-TEST matters for your use case — Microsoft Defender Antivirus is the better pick between these two.
Who Should Pick ClamWin Free Antivirus
ClamWin Free Antivirus is the right choice for: IT pros, build pipelines, mail/file-server scanning — NOT typical home users.
Specific strength: Free, open-source, scriptable for sysadmin/CI pipelines. Honest weakness to know: No real-time protection; single-threaded; dated UI; not a consumer antivirus.
If Open-source ClamAV engine + Windows frontend — not for typical consumers is the deciding factor in your buying decision, ClamWin Free Antivirus wins this comparison for your profile.
Frequently Asked Questions
Which has better detection, Microsoft Defender Antivirus or ClamWin Free Antivirus?
Both products have been independently tested. Microsoft Defender Antivirus scored 18/18 at AV-TEST February 2026 with Approved Windows Security Product Award. ClamWin Free Antivirus scored Not applicable (on-demand only) with Not applicable. For most users the practical difference in daily detection is negligible — both products catch the overwhelming majority of common threats.
Is Microsoft Defender Antivirus cheaper than ClamWin Free Antivirus?
Microsoft Defender Antivirus first year is Free (built into Windows 11/10) vs ClamWin Free Antivirus first year Free (GPL). Renewal: Free vs Free. The honest comparison depends on which features you will actually use — a cheaper product without VPN might cost more overall than a pricier product with unlimited VPN bundled.
Can I run Microsoft Defender Antivirus and ClamWin Free Antivirus together?
Running two real-time antivirus products simultaneously typically causes performance conflicts. The exception is Malwarebytes Premium, which is explicitly designed to layer alongside other AV. For any other pairing, pick one as primary.
Do both products work on Mac?
Microsoft Defender Antivirus platform coverage: Windows only. ClamWin Free Antivirus platform coverage: Windows. Pick based on which platforms you actually own devices for.
Which is the better pick in 2026?
The short answer depends on your situation. Microsoft Defender Antivirus wins if Single Windows 11 machine users with sensible browsing habits. ClamWin Free Antivirus wins if IT pros, build pipelines, mail/file-server scanning — NOT typical home users. Read the "Who Should Pick" sections above for the full decision logic.
Is either product safe to install?
Both are legitimate security products from established vendors. Microsoft Defender Antivirus is owned by Microsoft. ClamWin Free Antivirus is owned by Open-source (GNU GPL v2). Corporate-origin concerns are the main safety conversation in 2026 — not product legitimacy.
Final Verdict — Microsoft Defender Antivirus vs ClamWin Free Antivirus
Pick Microsoft Defender over ClamWin Free Antivirus if you are careful Windows 11 users with sensible browsing habits and no need for bundle features. Pick ClamWin Free Antivirus over Microsoft Defender if you are IT pros, build pipelines, mail/file-server scanning — NOT typical home users. On detection, AV-TEST 18/18 vs ClamAV signatures — verify current cycle on each vendor’s public report page. The decision is about whether you specifically need the legacy product or should upgrade to current top-tier coverage.
For full per-product details, see our individual deep-dive reviews: Microsoft Defender Antivirus review and ClamWin Free Antivirus review. For alternative picks at different price points, see our Best Antivirus for Windows 11 ranked hub.
