Understanding Signal Message Sync After Reinstall

This topic explains how message synchronization works between the Signal mobile app (CM for SGNL) and the Signal desktop app after a period of inactivity or reinstalling the mobile app.

• The mobile device is the primary device and source of encryption keys.

• Desktop devices are linked devices that sync messages from the mobile device.

• Messages are not synced from desktop back to mobile.

Standard Sync Behavior

• Signal desktop can remain linked and functional even if the mobile app is not opened regularly.

• A linked desktop can continue working for up to 30 days of mobile inactivity.

• Messages sent or received on Desktop during this period remain available only on the desktop until they are synced to mobile.

• Opening the mobile app within this window allows messages to sync normally.

Best practice

Open the Signal mobile application on a daily basis or more often to prevent any synchronization issues.

Updating the Mobile App

• A standard Signal app update does not break the desktop link.

• If messages are missing after an update, this may indicate a bug in the Signal app.

Reinstalling the Signal Mobile App

Reinstalling the Signal mobile app breaks the existing link between the mobile device and all linked desktops.

This happens because:

• The mobile app generates new encryption keys during reinstall.

• Previously linked desktop sessions are permanently disconnected.

• Messages that exist only on the desktop and were not synced to the mobile app:

  • Will not sync after reinstall

  • Will not reappear on the mobile app

  • Will not transfer to a newly linked desktop

Warning

Once the link is broken, desktop‑only messages are at risk of permanent loss unless manually preserved.

Re‑Linking Desktop After Reinstall

Before you close the old desktop session or re‑link:

1. Document missing messages

   • Take photos or a short video of the messages on the desktop.

2. Archive them into Signal

   • Send the images/videos into Signal (preferably into the original chat).

   • This preserves message context and contact metadata.

Only after this documentation is complete should you re‑link the desktop.

When you re‑link Signal desktop to a freshly installed mobile app:

• A new desktop session is created.

• Sync direction is mobile to desktop only.

• The desktop will sync up to 45 days of message history from the mobile app.

  Important

  • The 45‑day sync window applies only to messages already on the mobile app.

  • It does not recover:

    • Messages that existed only on the old desktop

    • Messages sent during the period when mobile was uninstalled

Example Scenario

Scenario

A user sends and receives messages on Signal Desktop for 3 days without opening the mobile app, then reinstalls the mobile app.

Result

• The desktop link is broken.

• Messages from those 3 days:

  • Will not sync to the mobile app

  • Will not appear after re‑linking

• After re‑linking:

  • New messages sync normally going forward

  • Up to 45 days of existing mobile messages sync to the new desktop

Summary of Sync

Best Practice for Signal Capture Users

• Open the CM for SGNL mobile app daily.

• Avoid long sync gaps between desktop and mobile.

• Do not reinstall the mobile app without first verifying message sync.

• Preserve desktop‑only messages before re‑linking.