How "Find Friends" Works Without Uploading Your Address Book

"Find friends on the app" is convenient, but uploading everyone's phone numbers to a company feels wrong. Hashed matching is a better approach.

#What a hash is

A hash is a one-way fingerprint. Feed in `+923001234567` and you get a long string like `a3f9…`. The same number always produces the same fingerprint, but you can't turn the fingerprint back into the number.

#How Yapie matches contacts

1. You allow access to contacts (on Android) or add phones/emails manually. 2. On your device, each phone number is **normalised** (e.g. to +92 format) and email lower-cased. 3. Each is turned into a **hash**. 4. Only the hashes are sent to the server, which compares them with hashes of users' verified phones and emails. 5. You see which contacts are on Yapie.

#"Contact joined Yapie" notifications

When someone in your synced contacts later verifies their phone or email on Yapie, you get a notification — so you can say hello.

#Limitations, honestly

Phone numbers come from a limited range, so a determined party could try hashing many numbers to reverse a hash. That's why hashing is a privacy **improvement**, not a perfect shield. Yapie uses hashes only for matching, and you can turn contact sync off any time.

#Your controls

- Sync is **optional** — find people by @username instead. - Turn sync off in **Settings**, and revoke the contacts permission in Android settings. - Control who can find and message you in **Settings › Privacy & security**.

#Frequently asked questions

Does Yapie upload my contacts?

Yapie sends one-way hashes of numbers and emails for matching, not your address book's names or raw numbers.

How do I know when a friend joins Yapie?

If you've synced contacts, Yapie notifies you when one of them verifies their phone or email.

Can I use Yapie without sharing contacts?

Yes. Search people by @username, email or phone instead.