WhatsApp is one of the most popular messaging apps but it has recently come under fire due to privacy concerns. Its parent company Facebook doesn’t have the best track record when it comes to privacy and its recent move to introduce ads into the app has left its userbase displeased.

This is where WhatsApp’s direct rival Signal comes in. The app only has 10 million downloads on the PlayStore so far, but the security and privacy it offers make it an attractive alternative. It has received several updates over the years and is no longer just a barebones encrypted messaging app, now rivaling some of the best apps out there.

It features messages, images, and videos that disappear after being viewed, akin to Snapchat and Instagram. It has also been announced that users will soon be able to save encrypted contact details onto the Signal server. This contact book is preserved for when a person wants to switch from one phone to another or wants to keep it entirely separate from the phone.

This contact information is encrypted and is not accessible by the phone’s operating system either. The developers believe that this may allow them to completely do away with phone numbers.

The app’s group chats use “anonymous credentials” to anonymize someone’s contact information for when they enter a group. Even Signal’s server itself will not be aware of people being added or removed from the group. Moxie Marlinspike, the creator of Signal and co-founder of the Signal Foundation, says:

It required coming up with some innovations in the world of cryptography. And in the end, it’s just invisible. It’s just groups, and it works like we expect groups to work.

The developers fear that adding more features to the app will make room for more vulnerabilities but they are also working to make it accessible for everyone and not just tech nerds.