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Signal is a cross-platform centralized encrypted instant messaging service developed by the Signal Technology Foundation and Signal Messenger LLC. Users can send one-to-one and group messages, which can include files, voice notes, images, and videos. It can also be used to make one-to-one and group voice and video calls, and the Android version can optionally function as an SMS app.

Quick Facts


  • Ranked #23,326th worldwide
  • Active users 40 M
  • Type Messaging Networks
  • Launched date Jul 29, 2014
  • Employees 180
  • Headquarters Mountain View, California, U.S.
  • Parent company Signal Technology Foundation (2018 - present)


Moxie Marlinspike Georgia
Brian Acton


  • Brand value In 2020 N/A
  • Revenue in 2020 $4.2 M
  • Net loss In 2020 N/A


BlockingIran blocks Signal App. (via

In Dec 2016, Egypt blocked access to Signal. In response, Signal's developers added domain fronting to their service. This allows Signal users in a specific country to circumvent censorship by making it look like they are connecting to a different internet-based service. As of Mar 2021, Signal's domain fronting is enabled by default in Egypt, the United Arab Emirates, Oman, Qatar, and Iran.

As of Jan 2018, Signal was blocked in Iran. Signal's domain fronting feature relies on the Google App Engine (GAE) service. This does not work in Iran because Google has blocked Iranian access to GAE in order to comply with U.S. sanctions.

In early 2018, Google App Engine made an internal change to stop domain fronting for all countries. Due to this issue, Signal made a public change to use Amazon CloudFront for domain fronting. However, AWS also announced that they would be making changes to their service to prevent domain fronting.

As a result, Signal said that they would start investigating new methods/approaches. Signal switched from AWS back to Google in Apr 2019.

In Jan 2021, Iran removed the app from app stores and blocked Signal. Signal was later blocked by China in Mar 2021.


SecurityEdward Snowden has vouched for the Signal app. (via

In Oct 2014, the Electronic Frontier Foundation (EFF) included Signal in their updated surveillance self-defense guide.

Former NSA contractor Edward Snowden has endorsed Signal on multiple occasions. In his keynote speech at SXSW in Mar 2014, he praised Signal's predecessors (TextSecure and RedPhone) for their ease of use.

In Dec 2014, Der Spiegel leaked slides from an internal NSA presentation dating to Jun 2012 in which the NSA deemed Signal's encrypted voice calling component (RedPhone) on its own as a "major threat" to its mission of accessing users' private data, and when used in conjunction with other privacy tools such as Cspace, Tor, Tails, and TrueCrypt was ranked as "catastrophic" and led to a "near-total loss/lack of insight to target communications [and] presence".

Following the 2016 Democratic National Committee email leak, it was reported by Vanity Fair that Marc Elias (the general counsel for Hillary Clinton's presidential campaign) had instructed DNC staffers to exclusively use Signal when saying anything negative about Republican presidential nominee Donald Trump.

In Mar 2017, Signal was approved by the sergeant at arms of the U.S. Senate for use by senators and their staff.

On 27 Sep 2019, Natalie Silvanovich, a security engineer working in Google's vulnerability research team at Project Zero, disclosed how a bug in the Android Signal client could let an attacker spy on a user without their knowledge.

In Feb 2020, the European Commission recommended that its staff use Signal. Following the George Floyd protests, which began in May 2020, Signal was downloaded 121,000 times in the U.S. between 25 May and 4 Jun.

In Jul 2020, Signal became the most downloaded app in Hong Kong on both the Apple App Store and the Google Play Store after the passage of the Hong Kong national security law.

As of Jan 2021, Signal is regarded as one of the best contact methods to securely provide tips to major news outlets such as The Washington Post, The Guardian, The New York Times, and The Wall Street Journal.

Original Idea

original ideaoriginal idea

On 21 Feb 2018, Moxie Marlinspike and WhatsApp co-founder Brian Acton announced the formation of the Signal Technology Foundation, a 501(c) nonprofit organization whose mission is "to support, accelerate, and broaden Signal's mission of making private communication accessible and ubiquitous".

Acton started the foundation with $50M in funding after leaving WhatsApp's parent company Facebook in Sep 2017. According to the announcement, Acton is the foundation's executive chairman and Marlinspike continues as the CEO of Signal Messenger. As of 2020, Signal ran entirely on donations, as a nonprofit.

Brief History

May Moxie Marlinspike and Stuart Anderson (Whisper Systems) launched TextSecure and RedPhone on Android.
Nov Whisper Systems was acquired by Twitter.
Dec TextSecure and RedPhone are released as free and open-source software under the GPLv3 license.
Jan Moxie Marlinspike left Twitter and founded Open Whisper Systems (OWS) as a collaborative open source project for the continued development of TextSecure and RedPhone.
Feb OWS added end-to-end encrypted group chat and instant messaging capabilities to TextSecure.
Jul OWS released Signal as a RedPhone counterpart for iOS.
Mar OWS discontinues support for encrypted SMS/MMS messaging in TextSecure while retaining its encrypted IM capabilities.

At the same time, OWS adds encrypted IM to Signal on iOS.

Nov RedPhone is merged into TextSecure on Android and the app is renamed as Signal.
Dec Signal Desktop is launched as a Chrome App.
Dec Egypt blocked access to Signal.
Mar OWS transitions Signal's calling system from RedPhone to WebRTC and adds the ability to make video calls with the mobile apps.

Signal was approved by the sergeant at arms of the U.S. Senate for use by senators and their staff.

Oct Announced the deprecation of their Chrome App and the release of a new Electron-based Signal Desktop.
Jan Signal was blocked in Iran.
Feb Moxie Marlinspike and Brian Acton launched the Signal Foundation with an initial $50M in funding from Acton.
Aug The Signal Protocol has been implemented into WhatsApp, Facebook Messenger, Skype, and Google Allo.
Nov Added support for iPads.
Feb Added view-once view-once images and videos, stickers, and reactions.
Aug Added message requests and one-to-one voice.
Oct Signal starts transitioning to a new encrypted group chat system with support for @mentions, group admins, and more granular permissions.
Dec Added video calling to Signal Desktop.

Added support for encrypted group calling.

Mar Signal was blocked by China.

Network Features

Your Signal Profile is a name, picture, and about that will be shown alongside your existing phone number when communicating with other users.

Signal allows users to make one-to-one and group voice and video calls with up to 8 people on iOS, Android, and desktop. All calls are made over a Wi-Fi or data connection and (with the exception of data fees) are free of charge, including long distance and international.

Signal also allows users to send text messages, files, voice notes, pictures, GIFs, and video messages over a Wi-Fi or data connection to other Signal users on iOS, Android, and a desktop app. The app also supports group messaging.

All communications between Signal users are automatically end-to-end encrypted (the encryption keys are generated and stored on the phones, not on the servers). To verify that a correspondent is really the person that they claim to be, Signal users can compare key fingerprints (or scan QR codes) out-of-band. The app employs a trust-on-first-use mechanism in order to notify the user if a correspondent's key changes.

Signal excludes users' messages from non-encrypted cloud backups by default.

Signal allows users to automatically blur faces of people in photos to protect their identities.

Block Screenshots

Block ScreenshotsBlock screenshots on Signal. (via

Like Snapchat, you can prevent other users from capturing screenshots of chats or anything inside the app.

With this option enabled, you can't even take screenshots from the recent chats menu, which adds an extra layer of privacy protection. The company offers this feature so that no information is relinquished to other users without your consent.

Send Disappearing Messages

Send Disappearing MessagesSend disappearing messages on Signal. (via

Being a privacy-oriented messaging service, Signal offers a ton of features that can help you have private and secure conversations. Every conversation has the capacity to enable Disappearing messages.

With disappearing messages turned on in Signal, you can essentially set a timer for when the messages disappear once both parties have read them.

Incognito Keyboard

Incognito KeyboardIncognito keyboard on Signal. (via

If you are worried about your keyboard learning your usage patterns or sensitive info from your texting, then Incognito keyboard is among the best features that Signal has to offer. Users can get Signal to disable personalized learning on your keyboard app when typing messages. This works with all major keyboards such as Swiftkey, Gboard, and more.

Note to Self

Previously, users did this by creating a single-member group to send notes to themselves. While it worked without any issues, Signal offers a simpler way to do this with the Note to Self feature, which works pretty well.

Enable Two-Factor Authentication

Enable Two-Factor AuthenticationEnable Two-Factor Authentication on Signal. (via

Enabling Two-Factor Authentication (2FA) is a good idea for any application and service if there’s an option for it. This becomes important as it makes sure that even if someone gets access to the verification code for your number, the intruder won’t be able to access your chats

WeChat also allows users to exchange contacts with people nearby via Bluetooth, as well as providing various features for contacting people at random if desired.

WeChat supports different instant messaging methods, including text message, voice message, walkie talkie, and stickers. Users can send previously saved or live pictures and videos, profiles of other users, coupons, lucky money packages, or current GPS locations with friends either individually or in a group chat.


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