A btapp file extension is related to the uTorrent software. It is used for its application files written for embedded browser. Install uTorrent to open *.btapp files. They probably cannot be converted to anything else. These are files for uTorrent App.
To open BTAPP files, install software supports them. The most common issue is lacking proper applications supporting BTAPP files. Go to uTorrent site, download tool, and install it. On top is a list of programs by operating system supported.
BTAPP files associate with μTorrent client. They store applications for μTorrent. These files use HTML and JavaScript. The applications extend functionality of μTorrent. μTorrent is free from Ludvig Strigeus and Serge Paquet.
BTAPP files relate to BitTorrent client μTorrent. They are for storing μTorrent applications. The applications are in HTML and JavaScript. They allow extending μTorrent’s functionality.
BitTorrent Client
uTorrent Client