Signal Desktop keeps its own encrypted copy of everything you receive
Attachments arrive on the Mac as well as the phone and stay there. Where the database is, and the setting that stops it growing forever.
Signal Desktop is a linked device rather than a window onto your phone, which means every message and attachment sent to you after linking is downloaded and stored locally, in its own encrypted database.
Where it is
du -sh ~/Library/Application\ Support/Signal 2>/dev/null
du -sh ~/Library/Application\ Support/Signal/* 2>/dev/null | sort -h | tail -8The attachments.noindex folder is usually the large one. The database itself holds message text, which is small, and the media is stored as individual encrypted files alongside it.
The setting that bounds it
Signal has a message retention option in its settings: keep messages forever, or for a year, or for a month. Setting it to anything other than forever converts an unbounded folder into a bounded one, and it applies to attachments as well as text.
Disappearing messages, set per conversation, do the same thing for individual chats and are the better tool where the conversation warrants it.
What deleting the folder does
| Action | Result |
|---|---|
| Set a retention period | Old messages and attachments removed on schedule |
| Delete a conversation in the app | Its attachments go with it |
| Remove the Signal folder | App unlinks, you relink and start fresh |
| Unlink the device on the phone | Local data becomes unusable |
The important line is the third: the desktop database is not backed up anywhere, so removing it loses the message history that exists only on the Mac. Your phone keeps its own copy of what it received, but the desktop history is not restored when you relink.
Compared with the others
WhatsApp and Telegram both keep server side copies, so clearing them locally costs nothing permanent. Signal is the exception in this group, because privacy by design means there is no server copy to restore from. Treat its folder accordingly.
Common questions
Where does Signal Desktop store messages on a Mac?
In ~/Library/Application Support/Signal, with an encrypted database for message text and an attachments.noindex folder for media. The attachments folder is usually the larger part.
How do I stop Signal Desktop using so much space?
Set a message retention period in settings, so messages and their attachments are removed after a month or a year, and use disappearing messages for individual conversations.
Is it safe to delete Signal's folder on a Mac?
It removes your desktop message history permanently, since there is no server side copy to restore from. The app unlinks and you start fresh after relinking, keeping only what arrives from then on.
Why does Signal use space when messages are on my phone?
Because a linked desktop is a full device, not a remote view. Everything sent to you after linking downloads to the Mac and is stored there in its own encrypted form.