.!QB File Extension
File TypeqBittorrent Partial Download File
What is a !QB file?
Incomplete download file created by qBittorrent, a Torrent client; appends the ".!qB" extension to a file as it's being downloaded, and the extension is removed when the download is complete; similar to .!BT BitTorrent and .!UT uTorrent files.
NOTE: The !QB extension is only used if you check the "Append .!qB extension to incomplete files" option in the Downloads settings (and then select Downloads). The option is unchecked by default.