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Duet Display vs OpenDisplay: catalog facts
Duet Display	OpenDisplay
Paid Paid app with plans listed on the pricing page.	Free Free and open source under GPL-3.0, with optional donations.
Windows, macOS, Android, iOS	macOS, iOS
Uses tablets and phones as extra monitors Drawing tablet mode for illustration	True extended display, not just mirroring Works over USB or Wi-Fi with touch and scroll input
Paid, with features split across plans Requires an account	Only extends Macs; Windows and Linux hosts are not supported Maintained by a single developer
Downloadable app	Downloadable app
Closed source	Open source
License not stated	License: GPL-3.0
Account needed	No account needed
Not stated if it works offline	Works offline
Official website Full listing and sources Checked October 1, 2026	Official website Full listing and sources Checked October 1, 2026

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