Opera 8.02 Technology Preview is available from the company's servers in versions for Windows, Linux and Mac OS.
Typically, BitTorrent downloads must be grabbed with a separate client, but this integration move makes Opera the first browser to build the capability into its own interface.
The popularity of BitTorrent is based on its ability to break large files into a number of smaller packets and distribute them among multiple users. Others then collect the file by retrieving it from several sources at the same time.
But the technology has achieved near Napster-like status due to its use for downloading free music, video and software. In May the FBI shut down one of the most high-profile BitTorrent sites, Elite Torrents.
But Opera maintains that it is an essential tool for meeting the growth in demand for the browser, and emphasises its legal usage.
"The true value of the technology became evident when the company launched Opera 8 in April this year," said Christen Krogh, vice president of engineering at Opera.
"The massive response, with more than 100 downloads per second, dealt a technical knock-out to Opera's servers. With BitTorrent, users would have had an alternative download mechanism."
Opera hopes to make it easier for users to download the large amount of legal material available, such as Linux software and computer game demos. The browser will also be offered for download as a torrent file.
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