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iPhone / Android · Flutter

Sector

Social, but only in person

There are no usernames to search and no invite links to forward. Only the people who are there with you can enter the same conversation. Posts are erased after 24 hours.

End-to-end encrypted with MLSErased after 24 hoursIn-person entry only
App StoreComing soonGoogle PlayIn progress

Preparing for App Store submission

Privacy PolicySupport

What it is

Three things

You join in person, or not at all

There are no remote friend requests. Whoever is inviting and everyone standing in the same place at that moment enter one sector together. There is no path for someone you have not met to enter your conversation.

Posts erase themselves

Every post is deleted from the server and from every device 24 hours after it is sent. Not hidden, not archived. There is no history left to hand over.

Built for being looked at

Sector normally shows a disk management screen. Put the phone face down and the conversation is covered instantly; coming back needs a deliberate tap. Notifications never show content either.

How it works

How joining works

Joining has three stages. Failing any one of them means you do not get in.

  1. 01

    Exchange keys

    The inviting device and the joining devices connect directly over Bluetooth and exchange encryption keys. The server plays no part in this.

  2. 02

    Match the code by eye

    The same code appears on every screen in the room. People confirming by eye that they match is what rejects a third party trying to sit in the middle.

  3. 03

    Confirm you are nearby

    Each joining location is compared against the inviter's to confirm everyone is within 100 meters. Solely for that confirmation, coordinates are sent to the server during the entrance procedure.

On devices that support it, UWB distance is also measured and recorded — but it is not used to decide whether you get in. The value is reported by the device, and the server has no way to verify it.

Honesty

What it cannot do

Here is what apps that sell privacy tend to leave out.

iOS cannot block screenshots

Public OS APIs do not let an app prevent a screenshot from being taken. Sector compensates by detecting screenshots and screen recording and covering the screen immediately. Android blocks capture itself, as far as the OS allows. This asymmetry cannot be removed.

Access logs are kept for 180 days

For the operator's legal defense, a hashed identifier, source IP address, timestamp, and sector number are retained for 180 days. Message contents are not included. Deleting your data does not remove them within that period.

UWB is advisory only

What decides proximity is a location check within 100 meters. UWB distance is recorded on devices that can measure it, but it is not used in the decision. Centimeter-scale distance can only be measured on the device, and the server cannot verify it.

Reporting sends the conversation to us

When you report a sector, the conversation stored on your device — including messages written by other participants — is sealed and sent to the developer. The server cannot read it, but the developer decrypts it locally to review. Reported data is retained as a record of the decision and is not deleted automatically.

Joining sends your coordinates

To confirm proximity, your latitude and longitude are sent to the server during the entrance procedure. The inviting device's coordinates are kept for 5 minutes and then discarded. The joining devices' coordinates are used only to compute the distance and are not stored. Location is not accessed at any other time.

Technology

What it is built on

Not a single algorithm here was designed by us. All of them are published standards.

Encryption
MLS (RFC 9420) — the IETF standard for encrypted group messaging
Server
Cloudflare Workers. It relays ciphertext and cannot read it — except when something is reported, as described above
On-device storage
SQLCipher encrypted database
Key exchange
Direct transfer over Bluetooth Low Energy plus a visual code check
Location
During the entrance procedure only. Inviter's coordinates kept 5 minutes
App
Flutter (iPhone / Android)

FAQ

Frequently asked questions

Do posts really disappear?
Yes. 24 hours after being sent, they are deleted from the server and from every device. They are not kept in backups.
Can screenshots be prevented?
On Android, capture and screen recording are blocked. On iOS the OS does not allow blocking capture itself, so Sector detects it and covers the screen. In neither case can it stop someone photographing the screen with another device.
How do I invite someone?
There is no friend-request function. Only the people who are there with you, and who go through the entrance procedure, end up in the same sector. It is not one-to-one — everyone present can be admitted at once.
Can you read my posts?
Normally no. Posts are end-to-end encrypted with MLS and the server holds only ciphertext. However, if someone reports that sector, that conversation reaches the developer.
Do I need an account?
No. No phone number, no email address. A random identifier generated by your device is the whole of your identity.
When can I use it?
The iPhone version is being prepared for App Store submission. The Android version is in progress.