PrismCipher For Chrome can be used to encrypt information over the following services:

• Google Gmail
• Yahoo! mail
• Outlook on the web
• ProtonMail
• Slack direct messages

PrismCipher should work flawlessly in any Chromium browser (blink engine), such as:
   Brave
   Chrome
   Chromium
   Edge
   Iridium
   Opera
   Ungoogled Chromium
   Vivaldi


Porting this over to a non-Chromium browser environment such as FireFox (gecko) or Safari (webkit) does not appear to be trivial. It’s planned, but won’t happen soon.