Signal (messaging app)
Also known as: Signal, Signal app, Signal Messenger, Signal Private Messenger
Signal is a free messaging app for texts, voice and video calls, and group chats, with end-to-end encryption on by default for everything.
It's run by the non-profit Signal Foundation and collects very little data about its users. Its encryption design, the Signal Protocol, is also used by WhatsApp and others. Signal supports disappearing messages, usernames that hide phone numbers, and post-quantum encryption. While Signal is widely recommended by security experts, encryption doesn't protect against adding the wrong person to a chat or a compromised phone.
Signal (messaging app), explained at three levels
At home
Signal is like sending letters in envelopes that only the recipient can open. Even the post office, Signal itself, can't read them.
At work
Signal is a strong choice for sensitive conversations, though businesses may need approved tools for record keeping.
At home
You can set a Signal username so people can contact you without your phone number. Disappearing messages can be set per chat.
At work
Signal's end-to-end encryption means messages can't be retrieved from servers, which may conflict with record-keeping obligations in regulated industries.
At home
Check who's in a group chat before sharing sensitive things. In my opinion, the biggest Signal risk is adding the wrong person, not broken encryption.
At work
Set policies on which messaging apps can be used for business, consider archiving requirements, verify safety numbers for high-risk contacts, and secure devices, since encryption doesn't protect an unlocked phone.
Real-world examples
At home
Lena's family switched their group chat to Signal for privacy. Her grandmother found it as easy to use as regular texting.
At work
Jerome's Regina MSP helped a journalist client set up Signal with disappearing messages and registration lock to protect sources.
How it compares
| feature | Signal (messaging app) | |
|---|---|---|
| End-to-end encryption | Always on | Always on for messages |
| Owned by | Non-profit foundation | Meta |
| Data collected | Very minimal | More metadata |
| User base | Smaller | Billions |
Both encrypt messages. Signal collects far less data.
For analysts
In communication policies, I'd specify which apps are allowed for business decisions and how records are kept. Encryption and retention needs must be balanced deliberately.
History & origin
Moxie Marlinspike and Stuart Anderson founded Whisper Systems, releasing the encrypted apps TextSecure and RedPhone in 2010. Twitter acquired the company in 2011, after which the projects continued as Open Whisper Systems. The Signal app launched on iPhone in 2014 and merged the earlier Android apps in 2015. WhatsApp adopted the Signal Protocol for its billion-plus users in 2016. WhatsApp co-founder Brian Acton helped create the Signal Foundation in 2018 with $50 million US. Signal added usernames in 2024 and post-quantum protection in 2023. In March 2025, senior US officials accidentally added a journalist to a Signal group chat discussing military plans, an episode showing how human error can undermine strong encryption. In my view, Signal sets the standard other messaging apps are measured against.