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Send to Kindle vs Calibre: catalog facts
Send to Kindle	Calibre
Free Free download from Amazon.	Free Free and open source, funded by donations.
macOS	Windows, macOS, Linux
Sends personal documents straight to a Kindle library Official Amazon tool	Converts between all the major ebook formats, including for Kindle Fetches metadata and covers from the internet automatically
Requires an Amazon account Only works with Kindle devices and apps	The interface is dense and has accumulated two decades of features It will not remove DRM; that requires third-party plug-ins with their own legal questions
Downloadable app	Downloadable app
Closed source	Open source
License not stated	License: GPL-3.0
Account needed	No account needed
Needs internet	Works offline
Official website Full listing and sources Checked October 1, 2026	Official website Full listing and sources Checked September 20, 2026

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