Cryptocat is an open source web and mobile application intended to allow secure, encrypted online chatting. Cryptocat uses end-to-end encryption and encrypts chats on the client side, only trusting the server with data that is already encrypted. Cryptocat is offered as an app for Mac OS X or as a browser extension for Google Chrome, Mozilla Firefox, Apple Safari, Opera and as a mobile app for iPhone.
Cryptocat's stated goal is to make encrypted communications more accessible to average users. The chat software aims to strike a balance between security and usability—offering more privacy than services such as Google Talk or Internet Relay Chat, while maintaining a higher level of accessibility than Pidgin. In June 2013, Cryptocat was used by journalist Glenn Greenwald while in Hong Kong to meet NSA whistleblower Edward Snowden for the first time, after other encryption software failed to work. In November 2013, Cryptocat was banned in Iran, shortly after the election of Iran's new president Hassan Rouhani who had promised more open Internet laws.
Cryptocat is developed by the Cryptocat team and is released under the GPLv3 license. In June 2014, Cryptocat was ranked first in a three-month study evaluating the security and usability of instant messaging encryption software, conducted by the German PSW Group.