Whisper Systems is acquired by Twitter,[2] "primarily so that Mr. Marlinspike could help the then-startup improve its security."[3]
Dec 2011 – Jul 2012
TextSecure and RedPhone are released as free and open-source software under the GPLv3 license.[4][5]
Jan 2013
Moxie Marlinspike leaves Twitter and founds Open Whisper Systems (OWS) as a collaborative open source project for the continued development of TextSecure and RedPhone.[6][7]
Feb 2014
OWS adds end-to-end encrypted group chat and instant messaging capabilities to TextSecure.[8]
Jul 2014
OWS releases Signal as a RedPhone counterpart for iOS.[9][10]
Mar 2015
OWS discontinues support for encrypted SMS/MMS messaging in TextSecure, while retaining its encrypted IM capabilities.[11] At the same time, OWS adds encrypted IM to Signal on iOS.[12]
Nov 2015
RedPhone is merged into TextSecure on Android and the app is renamed as Signal.[13]
OWS announces the deprecation of their Chrome App and the release of a new Electron-based Signal Desktop.[15]
Mar 2017
OWS transitions Signal's calling system from RedPhone to WebRTC and adds the ability to make video calls with the mobile apps.[16][17]
Feb 2018
Moxie Marlinspike and Brian Acton launch the Signal Foundation with an initial $50 million in funding from Acton, who had left WhatsApp's parent company Facebook in September 2017.[18][19]
Nov 2019 – Feb 2020
Signal adds support for iPads,[20] view-once images and videos, stickers, and reactions.[21]
Aug 2020 – Sep 2020
Signal adds message requests[22] and one-to-one voice and video calling to Signal Desktop.[23][24]
Oct 2020 – Dec 2020
Signal starts transitioning to a new encrypted group chat system with support for @mentions, group admins, and more granular permissions.[25] It also adds support for encrypted group calling.[25]
