What to Know About Signal, the Private Messaging App Even Cybersecurity Experts Use

Updated: Dec. 08, 2023

Signal private messenger app is a favorite of government officials, tech giants, and cyber experts. Find out why.

Concerned about your privacy when texting or making phone calls? Signal is a popular secure private messaging app that everyone from Twitter founder Jack Dorsey to whistleblower Edward Snowden use, according to the app’s website. It has also gained popularity during the recent pandemic and during protests as a way to communicate safely. Even WhatsApp uses Signal’s open-source safety protocols for its own app.

Thinking about using it for yourself? Here’s everything you need to know about Signal, from how to use it, to the details on just how safe it is to use.

What is Signal?

Signal private messenger

Signal is a free private messaging app that you can use to:

  • send text messages
  • send photos
  • send voice messages
  • make calls
  • make video calls

One of the biggest reasons Signals is so popular is that it uses end-to-end encryption that prevents others, including the government, from accessing and monitoring messages. Also, messages are stored locally, on your device, not in the cloud. This means that the company isn’t storing—and potentially sharing—your private messages. Signal also doesn’t access your private data, share your information in the cloud, or accept advertising. We’ll talk more about Signal’s safety features later.

Signal for iOS and Android

Signal is available for both iOS and Android and also available to download on your PC or Mac. You can download Signal directly from the Signal download page, the Apple Store if you have an iPhone, or Google Play if you have an Android.

How Signal works

Signal encryption

Both calls and messages sent through the Signal app have end-to-end encryption. What this means is that your message is encrypted in the app before it is sent out to your network and the internet. It remains encrypted until it reaches the recipient, where it is decrypted inside of the recipient’s app. “This provides a higher level of security than previous generations of messaging apps, that only provided encryption in the form of HTTPS,” explained Cody Beers, technical training manager at WhiteHat Security. No one, not even Signal, can see your messages except for the person you send the message to.

It’s important to note, however, that this encryption only works if the person you’re sending the message to also uses Signal if they use an Android device. (On Apple devices, all messages are encrypted, no matter if the recipient is using Signal or not.) You’ll know if you see a locked icon next to the send button after you enter the recipient’s phone number.

Signal features

Signal has everything you want in a good messaging app, including:

  • Group chats. Group chats on Signal can have up to 150 participants. For comparison’s sake, iPhones can have a max of 25 participants, depending on your carrier that number may be as low as ten.
  • View-once Media. You can choose to have a photo or video disappear after the recipient(s) see it. Unlike other apps, Signal prevents the recipient from taking a screenshot of your image. It’s still possible, of course, that someone may take a photo of the message using a different phone or camera, so you still need to think twice before sending anything truly private.
  • Photo editing. Some editing features within the app include adding text, drawing, face blurring (helpful if you want to conceal someone’s identity in a photo), and stickers.
  • Additional media and information. You can add emojis, GIFs, contact information, voice messages, or your location to any message
  • Note to Self. Instead of choosing a person from the contacts list, you can choose “Note to Self,” which essentially sends messages to yourself. The note will be sent to all of your devices that are linked to your Signal account.

Is Signal safe?

Signal prides itself on keeping you and your information safe in several different ways. For one, “Signal is also an open-source app, meaning the code can be reviewed by anyone to make sure there are no flaws in the app and its system,” says Chris Hauk, consumer privacy champion at Pixel Privacy.

Additionally, Signal says that it does not “collect or store any sensitive information. “Signal messages and calls cannot be accessed by us or other third parties because they are always end-to-end encrypted, private, and secure.” Another plus is that it doesn’t accept advertisements, so it “doesn’t share your info with advertisers or any other Nosy Nellies,” adds Hauk.

A measure you can take to keep it as safe as possible is to lock the app so that it can only be opened by your phone’s screen lock password or fingerprint. You can even prevent your phone’s keyboard from using its AI learning features when you have the app open by changing your privacy settings.

Can Signal be tracked?

Signal not only encrypts messages, but it also hides virtually all metadata associated with the message, including who sent the message, Hauk explains. “That means only the person who sent the message or received the message knows who the sender is,” he says.
Even with all of these security features, just like with other apps, it isn’t 100 percent secure. While Signal makes it harder for hackers, the app can potentially be hacked through spyware apps. These apps can log keystrokes and take screenshots of other apps, making it possible for a hacker to monitor a Signal conversation.

Can Signal messages be retrieved?

“Signal does not store messages, conversation histories, or encryption keys in the cloud, the messages are stored only on the user’s device in an encrypted format,” says Hauk. Since messages and calls are stored locally on your device instead of the cloud, Signal has no way to retrieve your messages if your phone is lost or stolen, nor can they turn them over to law enforcement.

Next, read on to learn the top security threats to mobile phones in 2021.