Signal is a
cross-platform centralized
Centralisation or centralization (see spelling differences) is the process by which the activities of an organisation, particularly those regarding planning and decision-making, framing strategy and policies become concentrated within a particu ...
encrypted instant messaging service developed by the non-profit
Signal Foundation
The Signal Foundation, officially the Signal Technology Foundation, is an American non-profit organization founded in 2018 by Moxie Marlinspike and Brian Acton. Its mission is "to develop open-source privacy technology that protects free expres ...
and its subsidiary, the
Signal Messenger LLC
The Signal Foundation, officially the Signal Technology Foundation, is an American non-profit organization founded in 2018 by Moxie Marlinspike and Brian Acton. Its mission is "to develop open-source privacy technology that protects free expressi ...
. Users can send one-to-one and group messages, which can include
files
File or filing may refer to:
Mechanical tools and processes
* File (tool), a tool used to ''remove'' fine amounts of material from a workpiece
**Filing (metalworking), a material removal process in manufacturing
** Nail file, a tool used to gent ...
, voice notes,
images and
videos
Video is an electronic medium for the recording, copying, playback, broadcasting, and display of moving visual media. Video was first developed for mechanical television systems, which were quickly replaced by cathode-ray tube (CRT) syste ...
.
It can also be used to make one-to-one and group
voice and
video calls.
The
Android
Android may refer to:
Science and technology
* Android (robot), a humanoid robot or synthetic organism designed to imitate a human
* Android (operating system), Google's mobile operating system
** Bugdroid, a Google mascot sometimes referred to ...
version also optionally functions as an
SMS
Short Message/Messaging Service, commonly abbreviated as SMS, is a text messaging service component of most telephone, Internet and mobile device systems. It uses standardized communication protocols that let mobile devices exchange short text ...
app
App, Apps or APP may refer to:
Computing
* Application software
* Mobile app, software designed to run on smartphones and other mobile devices
* Web application or web app, software designed to run inside a web browser
* Adjusted Peak Performan ...
, but this functionality will be removed in 2023.
Signal uses standard cellular
telephone numbers as identifiers and secures all communications to other Signal users with
end-to-end encryption. The client software includes mechanisms by which users can independently verify the identity of their contacts and the integrity of the data channel.
Signal's software is
free and open-source
Free and open-source software (FOSS) is a term used to refer to groups of software consisting of both free software and open-source software where anyone is freely licensed to use, copy, study, and change the software in any way, and the source ...
. Its
mobile
Mobile may refer to:
Places
* Mobile, Alabama, a U.S. port city
* Mobile County, Alabama
* Mobile, Arizona, a small town near Phoenix, U.S.
* Mobile, Newfoundland and Labrador
Arts, entertainment, and media Music Groups and labels
* Mobile ...
clients are published under the
GPL-3.0-only license
A license (or licence) is an official permission or permit to do, use, or own something (as well as the document of that permission or permit).
A license is granted by a party (licensor) to another party (licensee) as an element of an agreeme ...
,
while the
desktop client and
server
Server may refer to:
Computing
*Server (computing), a computer program or a device that provides functionality for other programs or devices, called clients
Role
* Waiting staff, those who work at a restaurant or a bar attending customers and su ...
are published under the
AGPL-3.0-only license.
The official Android app generally uses the proprietary
Google Play Services (installed on most Android devices), though it is designed to still work without them installed. Signal also has an official client app for
iOS and desktop programs for
Windows,
macOS and
Linux (although registration requires an iOS or Android device).
The
non-profit Signal Foundation was launched in February 2018 with initial funding of $50 million from
Brian Acton
Brian Acton (born 1972/1973) is an American computer programmer and Internet entrepreneur. Acton is the executive chairman of the Signal Technology Foundation, which he co-founded with Moxie Marlinspike in 2018. , Acton also serves as interim C ...
.
, the platform had approximately 40 million monthly active users. , it was downloaded more than 105 million times.
History
2010–2013: Origins
Signal is the successor of the RedPhone encrypted voice calling app and the
TextSecure
TextSecure was an encrypted messaging application for Android that was developed from 2010 to 2015. It was a predecessor to Signal and the first application to use the Signal Protocol, which has since been implemented into WhatsApp and other app ...
encrypted texting program. The
beta versions of RedPhone and TextSecure were first launched in May 2010 by
Whisper Systems
Whisper Systems was an American enterprise mobile security company that was co-founded by security researcher Moxie Marlinspike and roboticist Stuart Anderson in 2010. The company was acquired by Twitter in November 2011. Some of the company's s ...
,
a startup company co-founded by security researcher
Moxie Marlinspike and roboticist Stuart Anderson.
Whisper Systems also produced a firewall and tools for encrypting other forms of data.
All of these were