Snapshots are not available in Briefer’s open-source version.

How to open the snapshots panel.

The snapshots panel.
Restoring a snapshot
To restore a snapshot, click on the desired snapshot in the snapshots panel. This will open a preview of the snapshot, where you can see the page’s content at that point in time. Then, click on the “Restore” link on the top banner of the snapshot preview. This will restore the page to the state it was in when the snapshot was taken.
Click the "restore" link to restore the page to the snapshot's state.