Compare ClamWin vs Windows Defender
ClamWin Free Antivirus vs Microsoft Defender Antivirus at a Glance
Comparing ClamWin Free Antivirus and Microsoft Defender 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.
ClamWin Free Antivirus — Free, open-source, scriptable for sysadmin/CI pipelines. Owned by Open-source (GNU GPL v2). First year: Free (GPL), renewal: Free.
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.
Quick Verdict Table
| ClamWin Free Antivirus | Microsoft Defender Antivirus | |
|---|---|---|
| First-year price | Free (GPL) | Free (built into Windows 11/10) |
| Renewal | Free | Free |
| Devices | 1 device | 1 Windows PC per license |
| Platforms | Windows | Windows only |
| AV-TEST Feb 2026 | Not applicable (on-demand only) | 18/18 |
| AV-Comparatives 2025 | Not applicable | Approved Windows Security Product Award |
| Key differentiator | Open-source ClamAV engine + Windows frontend — not for typical consumers | Free built-in baseline now scoring 18/18 at AV-TEST |
| Corporate owner | Open-source (GNU GPL v2) | Microsoft |
Lab Test Showdown
ClamWin Free Antivirus lab results: Not applicable (on-demand only) at AV-TEST February 2026. Not applicable at AV-Comparatives 2025 Summary Report.
Microsoft Defender Antivirus lab results: 18/18 at AV-TEST February 2026. Approved Windows Security Product Award.
What this means for you: Lab scores measure whether the product catches known and unknown malware samples in controlled conditions. Both ClamWin Free Antivirus and Microsoft Defender 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
ClamWin Free Antivirus: Free (GPL) first year, Free at auto-renewal. Free, open-source, scriptable for sysadmin/CI pipelines
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
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 | ||
ClamWin Free Antivirus feature set:
- ClamAV engine (Cisco Talos)
- Scheduled scans
- Explorer context-menu integration
- Outlook add-in
Microsoft Defender Antivirus feature set:
- Real-time protection
- SmartScreen web filter
- Controlled Folder Access (ransomware)
- Exploit Guard
- Cloud-delivered protection
The feature difference reflects the products' different positioning: Open-source ClamAV engine + Windows frontend — not for typical consumers versus Free built-in baseline now scoring 18/18 at AV-TEST. 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.
| ClamWin Free Antivirus | Microsoft Defender Antivirus | |
|---|---|---|
| Idle RAM footprint | N/A (on-demand) | 55-90 MB |
| CPU peak during full scan | 15-25% (on-demand) | 18-28% |
| Full scan duration | 46 min (single-threaded) | 14 min |
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 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 your priorities align with that profile — and especially if Open-source ClamAV engine + Windows frontend — not for typical consumers matters for your use case — ClamWin Free Antivirus is the better pick between these two.
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 Free built-in baseline now scoring 18/18 at AV-TEST is the deciding factor in your buying decision, Microsoft Defender Antivirus wins this comparison for your profile.
Frequently Asked Questions
Which has better detection, ClamWin Free Antivirus or Microsoft Defender Antivirus?
Both products have been independently tested. ClamWin Free Antivirus scored Not applicable (on-demand only) at AV-TEST February 2026 with Not applicable. Microsoft Defender Antivirus scored 18/18 with Approved Windows Security Product Award. For most users the practical difference in daily detection is negligible — both products catch the overwhelming majority of common threats.
Is ClamWin Free Antivirus cheaper than Microsoft Defender Antivirus?
ClamWin Free Antivirus first year is Free (GPL) vs Microsoft Defender Antivirus first year Free (built into Windows 11/10). 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 ClamWin Free Antivirus and Microsoft Defender 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?
ClamWin Free Antivirus platform coverage: Windows. Microsoft Defender Antivirus platform coverage: Windows only. Pick based on which platforms you actually own devices for.
Which is the better pick in 2026?
The short answer depends on your situation. ClamWin Free Antivirus wins if IT pros, build pipelines, mail/file-server scanning — NOT typical home users. Microsoft Defender Antivirus wins if Single Windows 11 machine users with sensible browsing habits. 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. ClamWin Free Antivirus is owned by Open-source (GNU GPL v2). Microsoft Defender Antivirus is owned by Microsoft. Corporate-origin concerns are the main safety conversation in 2026 — not product legitimacy.
Final Verdict — ClamWin Free Antivirus vs Microsoft Defender Antivirus
Pick ClamWin Free Antivirus over Microsoft Defender if you are IT pros, build pipelines, mail/file-server scanning — NOT typical home users. Pick Microsoft Defender over ClamWin Free Antivirus if you are careful Windows 11 users with sensible browsing habits and no need for bundle features. On detection, ClamAV signatures vs AV-TEST 18/18 — 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: ClamWin Free Antivirus review and Microsoft Defender Antivirus review. For alternative picks at different price points, see our Best Antivirus for Windows 11 ranked hub.
