Mailvelope is a browser extension for email encryption via webmail clients.
Compatible with clients such as Gmail and Roundcube.
Supports client-side encryption via PGP/GPG.
Supports Firefox, Edge, and Chrome browsers.
PGP: https://wikipedia.org/wiki/Pretty_Good_Privacy
GPG: https://wikipedia.org/wiki/GNU_Privacy_Guard
Client-side encryption: https://wikipedia.org/wiki/Client-side_encryption
Website: https://mailvelope.com
Mastodon: @mailvelope