μTorrent

µTorrent (uTorrent) is a free BitTorrent client for Microsoft Windows written in C++^[1] and localized for many different languages. It is designed to use minimal computer resources while offering functionality comparable to larger BitTorrent clients such as Azureus or BitComet.

The program has received consistently good reviews for its feature set, performance, stability, and support for older hardware and versions of Windows. It has been in active development since its first release in 2005. Its name is commonly abbreviated "µT" or "uT".

On December 7, 2006, µTorrent developer Ludvig Strigeus and BitTorrent, Inc. CEO Bram Cohen announced that BitTorrent, Inc. had acquired µTorrent.^[2] BitTorrent, Inc. has employed the code as the basis of version 6.0 of the BitTorrent client which makes it a re-branded version of µTorrent.

History

Early development

Out of general discontent with bloatware, Serge Paquet suggested to Ludvig Strigeus that he make a small and efficient BitTorrent client. Strigeus began to conceptualize the plans for the program's development, which, at the time, did not include making the client feature-rich. After initially working on it for about a month during the autumn of 2004 (the first build is dated October 17, 2004), mostly during his free time before or after work, Strigeus ceased coding µTorrent for a year. He resumed work on September 15, 2005, and three days later, the first public release (version 1.1 beta) was made available as freeware, and began generating feedback.

Pronunciation

"You" (u) or "Micro" (μ)

The author of µTorrent wrote in 2005, "I usually say 'you torrent' because it looks like a u", and offered "microtorrent" and "mytorrent" as candidate pronunciations.^[3] The symbol μ, which is actually the small Greek letter Mu, stands for the SI prefix "micro" meaning one one-millionth and refers to the program's small footprint.

PeerFactor SARL

On March 4, 2006, PeerFactor SARL^[4] announced the signing of a six-month contract with Strigeus for the development of "new content distribution applications on the Web."^[5] PeerFactor SARL is a relatively new company formed by former employees of PeerFactor, which was a subsidiary of the French anti-piracy organization Retspan.

Ludde stated that his coding for PeerFactor SARL was to use his expertise at optimization of the BitTorrent protocol to create a .dll which PeerFactor SARL intended to use as part of a distribution platform for files in a corporate setting.^[6] At the time there was some speculation that μTorrent may have been modified to spy on users on Peerfactor's behalf ^{[7] [8]}, however to date (even following μTorrent's acquisition by BitTorrent, Inc.) no evidence has been produced to support these allegations.

Ownership change

On December 7, 2006, µTorrent was purchased by BitTorrent, Inc., as it was announced on their official forum.^[2] µTorrent will continue to have its own website and community for now, and the µTorrent code base will remain closed source. Ludvig Strigeus, the writer of µTorrent, will serve as a technical consultant, but BitTorrent, Inc. will do the majority of the development work.^[9]

On September 18, 2007, BitTorrent 6.0 was released, which is a re-branded version of µTorrent. As a result, BitTorrent 6 is closed-source (unlike BitTorrent 5.x and before, which were open source software); and is currently only available for Windows.

Contributors

Original development was performed by Ludvig Strigeus ("ludde", from Sweden), the creator of µTorrent. Serge Paquet ("vurlix", from Canada) acted as release coordinator, and had intended to work on Linux and Mac OS X ports. He maintained the µTorrent website and forum up until the end of 2005, but is no longer affiliated with µTorrent.

Development after the purchase by BitTorrent is performed by developers Greg Hazel ("alus"), Arvid Norberg ("arvid", author of libtorrent), Jan Brittenson ("CodeRed"), Richard Choi ("rchoi") and Ryan Norton ("RyanNorton") at BitTorrent Inc. Strigeus remains as a technical consultant.

Other tasks continue to be performed by ongoing contributors. Giancarlo Martínez ("Firon", from Puerto Rico) maintains the µTorrent forums and FAQ. Timothy Su ("ignorantcow", from Malaysia) is the current website designer. Carsten Niebuhr ("Directrix", from Germany) developed and maintains the µTorrent Web User Interface.

Features

Features present in µTorrent include:

• µTorrent can use as little as 14 MB of RAM running on a 486 processor on Windows 95.^[10]
• Unicode support for Windows 95/98/ME, avoiding use of the Microsoft Layer for Unicode which is several times larger than µTorrent.
• UPnP support for all versions of Windows, without needing Windows XP's UPnP framework.
• Protocol encryption (PE),
• Peer exchange (PEX) with other µTorrent clients,
  • libtorrent and clients based on it (MooPolice, Deluge, etc.) have full µTorrent PEX support.
  • Transmission and clients based on libTransmission have full µTorrent PEX support.
  • KTorrent has full µTorrent PEX support as of 2.1 RC1.
  • Azureus has full support as of version 3.0.4.3
• RSS ("broadcatching").
• "Trackerless" BitTorrent support using DHT, compatible with the original BitTorrent client and BitComet.
• User configurable intelligent disk caching system.
• Full proxy server support.
• HTTPS tracker support.
• Configurable bandwidth scheduler.
• Localized for 38 languages.^[11]
• Initial seeding of torrents.
• Customizable search bar & user interface design^[12]
• Configuration settings and temporary files are stored in a single directory, allowing portable use.
• WebUI - A plugin currently in beta testing that allows µTorrent running on one computer to be controlled from another computer, either across the internet or on a LAN, using a Web page.
• Embedded Tracker - a simple tracker designed for seeding torrents, lacking a web interface or list of hosted torrents. It is not designed for secure or large-scale application.^[13]

Size

Version	Build	Release Date	Size
1.0.0			77 kB
1.1.7	293	2005-10-22	98 kB
1.2.2	345	2005-11-25	107 kB
1.3.0	364	2005-12-10	115 kB
1.4.0	402	2006-01-11	130 kB
1.5.0	437	2006-03-08	155 kB
1.6.1	490	2007-02-15	173 kB
1.7.7	8179	2008-01-25	214 kB

µTorrent is shipped as a single stand-alone compressed executable file, and does not require installation, though an installer is available for trivial installation. Recent versions have included the ability to install themselves on first run. Small executable size is achieved by avoiding the use of many libraries, notably the C++ standard library and stream facilities, and creating substitutes written specifically for the program. The executable is then compressed to roughly half of its compiled and linked size using UPX.