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Gpg4win vs Mailvelope: catalog facts
Gpg4win	Mailvelope
Free Free software, funded by donations and public contracts.	Free Free and open source for personal use. Business products are paid.
Windows	Browser extension
Kleopatra gives GnuPG a real key manager instead of a command line Integrates with Outlook through GpgOL and with Explorer through GpgEX	Works inside existing webmail rather than requiring a desktop mail client Keys stay in the browser under your control
Windows only OpenPGP key management is genuinely hard, and the concepts do not hide well behind a GUI	Only supports a defined list of webmail sites Browser-based key storage is weaker than a dedicated client or smartcard
Downloadable app	Browser extension
Open source	Open source
License: GPL-2.0	License: AGPL-3.0
No account needed	Not stated if an account is needed
Works offline	Not stated if it works offline
Official website Full listing and sources Checked September 20, 2026	Official website Full listing and sources Checked September 22, 2026

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