The app has no ads, does not track users' data, and does not store any metadata such as timestamps, internet addresses or group names so it can't give them up if asked. It is considered one of the most secure systems in the world. A company called Whisper Systems created two encrypted apps, RedPhone for voice calls and TextSecure for texting.

Signal is a free app that cybersecurity experts consider to be one of the most secure messaging services because of its end-to-end encryption. Simply put, text messages or calls are seen only by you, the sender and whoever is in your Signal group chat.

The chat app, which is run by a nonprofit foundation, has been downloaded 220 million times. Here’s what to know about Signal, including who owns it and whether it’s safe to use.