Why a messenger shouldn't need your phone number

For more than a decade, the phone number has been the default login for messaging. You type it in, receive a code, and your contacts magically appear. It is convenient, and it is why so many messengers grew so fast. But it comes at a cost to privacy that most people never think about. Here is why we believe a private messenger shouldn't need your phone number at all.

A phone number is an identity, not just an address

In many countries you must show ID to buy a SIM card, so carriers know the legal name behind each number. Even where that isn't required, your number tends to follow you for years and ends up attached to your bank, your online shopping, your delivery apps and your social media. It is one of the most reused personal identifiers there is.

When a messenger uses that number as your account, your messaging life becomes linkable to all of the above. End-to-end encryption may protect what you say, but the account itself points straight at you.

Five ways phone numbers leak privacy

1. Anyone who has your number can find you

If someone has your number, from a business card, a data leak or a group chat, they can often look you up and see a name, photo or online status. You never chose to be findable by them.

2. Groups spread it

In many apps, joining a group shows your phone number to every member, including strangers in large community groups.

3. Contact uploads include people who never signed up

To show you which friends use an app, it may upload the phone numbers in your address book. That includes people who never agreed to anything. Your number may already be in a messaging company's systems because someone else installed an app.

4. SIM swapping

Attackers can persuade or bribe carrier staff to move your number to a new SIM. Once they control the number, SMS verification codes go to them. Messengers add PINs and other protections, but the number is still a weak link.

5. Data requests are easy to target

A phone number is a perfect key for linking records. Asking a provider “what do you have on this number?” is simple, and the answer can be cross-referenced with carrier data.

“But I can hide my number now”

Some messengers now let you set a username and hide your number from other users. That is a real improvement for everyday privacy, and worth turning on. But the number is still required to register, still held by the provider, and still the anchor of the account. Hiding something from other users is not the same as not collecting it.

Why messengers use phone numbers anyway

To be fair, there are reasons. Phone numbers make spam harder, because each account costs a SIM. They make finding friends effortless. And they give an easy recovery path: if you lose your phone, an SMS gets you back in. Any messenger that drops phone numbers has to solve these problems another way.

How a username-only messenger solves them

• Spam: Frozen Chat asks new accounts to solve a small proof-of-work puzzle, which is cheap for one person and expensive for a bot farm, and accounts need a licence key.
• Finding friends: you share a username or QR code. It takes a moment longer, and you decide exactly who can reach you.
• Recovery: instead of SMS, you get a 24-word Recovery Key and set a recovery PIN. They are shown and stored only on your side, which also means no carrier employee can hand your account to someone else.

No phone number is only the start

Removing the phone number matters most when the rest of the system also avoids collecting identifying data. In Frozen Chat there is no e-mail either, the address book is never uploaded, the server is not told who sent a message (sealed sender), and no IP addresses are logged. Messages, groups and calls are end-to-end encrypted with post-quantum keys. Our page on a private messenger without a phone number walks through how sign-up works, and the security page lists the limits.

Who benefits most

Everyone benefits from collecting less, but some people especially: journalists and their sources, activists, people leaving abusive relationships, anyone who has had their number leaked or doxxed, and professionals who want to talk to clients without handing out a personal number. If that sounds like you, try the getting started guide or see how we compare with Signal, which is excellent but still needs a number.