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ClamAV vs Microsoft Defender: catalog facts
ClamAV	Microsoft Defender
Free Free and open source under the GPL 2.0, maintained by Cisco Talos.	Paid Included with a paid Microsoft 365 subscription, with a free trial available.
Windows, macOS, Linux, Command line	Windows, macOS, Android, iOS
Signature format is open, so anyone can write detections Designed to be embedded in mail servers, file shares and upload pipelines	Manages security for several family members and devices from one dashboard Dark web monitoring for more than 60 types of personal information
Detection rates trail the commercial engines in independent testing Not a real-time desktop protection suite on its own	Requires a Microsoft account and a Microsoft 365 subscription Closed source, with protection tied to Microsoft's cloud services
Downloadable app	Downloadable app
Open source	Closed source
License: GPL-2.0	License not stated
No account needed	Account needed
Works offline	Not stated if it works offline
Official website Full listing and sources Checked September 21, 2026	Official website Full listing and sources Checked September 23, 2026

Catalog facts only. Anything “not stated” is unconfirmed. Check full listings for details.