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Android

Getting Started

This guide walks you through installing the Semafore app on an Android device, signing in for the first time, and registering your device so your organisation administrator can approve you.

Before you begin

You will need:

  • An Android device running Android 8.0 (Oreo) or later
  • The phone number your organisation administrator used to invite you
  • Access to SMS on that phone number (to receive your sign-in code)

Your administrator must invite you by phone number before you can join. If you have not received an invitation or are unsure whether you have been invited, contact your Semafore administrator.

Step 1 — Download Semafore

Open the Google Play Store on your Android device and search for Semafore. Tap Install to download and install the app.

Alternatively, your administrator may send you a direct link.

Step 2 — Sign in with your phone number

Open Semafore. You will see a phone number entry screen.

Enter the phone number your administrator invited. Include the country code — for example, +44 7700 900001 for a UK number.

Tap Send code. You will receive a six-digit SMS code within a few seconds.

Enter the code. Semafore verifies it and creates your account.

Semafore uses phone-number authentication. There is no separate username or password. Your phone number is your identity on the platform.

Step 3 — Device registration

After sign-in, Semafore registers your device with your organisation. This happens automatically. You do not need to do anything.

Your organisation administrator will see your device appear in the portal Members list with status Registered. They must approve your account before you can send or receive messages.

This is intentional. Approval is a deliberate administrative step — it confirms to your organisation that it was you who signed in, not someone else using your phone number.

Step 4 — Wait for approval

You will see a Waiting for approval screen while your administrator reviews and approves your device registration.

Once your administrator approves you, the app moves to the messaging interface automatically. You do not need to restart the app.

If you have been waiting for more than a few minutes, contact your administrator directly — they may not have seen the notification.

Step 5 — You are ready

Once approved, you can:

  • Start a private message thread with any other approved member of your organisation
  • Be added to group threads by your administrator
  • Receive broadcasts sent by administrators to all members

All messages are encrypted on your device before they leave. Semafore’s server routes the encrypted data but cannot read it. Your organisation’s administrator can see that messages were sent (in the audit log) but not their content.

Push notifications

Semafore uses silent push notifications via Firebase Cloud Messaging to wake the app when a new message is waiting. The notification itself contains no message content — it is a signal to the app to reconnect and decrypt locally.

Allow Semafore to send you notifications when Android prompts you. If you declined the prompt, go to Settings → Apps → Semafore → Notifications and enable them. Without notifications, the app will not wake in the background when new messages arrive — you will still receive messages when you open the app manually.

Battery optimisation

Android’s battery optimisation settings can prevent background apps from receiving push notifications promptly. If you notice delayed message delivery:

Go to Settings → Apps → Semafore → Battery and select Unrestricted or Don’t optimise. The exact label varies by Android version and device manufacturer.

Troubleshooting

I did not receive an OTP code. Check that you entered the correct phone number with the full country code. SMS delivery can occasionally take up to 60 seconds. If the code still does not arrive, tap Resend code.

The app shows “Waiting for approval” for a long time. Your administrator needs to approve your device registration in the portal. Contact them directly.

I registered a new device and can no longer access my messages on my old device. Each device registration is independent. Your messages are stored locally on each device and encrypted with keys specific to that device. Messages sent before you registered the new device are not automatically available on it.

Messages are delivered late or only when I open the app. Android battery optimisation is likely restricting Semafore’s background activity. See the Battery optimisation section above.

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