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A 3D look logo released with version 3.3 on May 22, 2013.
µTorrent 3.3.2 on Windows 7 64-bit
Original author(s) Ludvig Strigeus
Developer(s) BitTorrent, Inc.
Initial release September 18, 2005 (2005-09-18)
Stable release

Microsoft Windows:
3.4.5 (Build 41202) (October 6, 2015 (2015-10-06)) [1][2]
OS X for Intel:
1.8.7 (Build 41266) (October 29, 2015 (2015-10-29)) [3][4]
OS X for PPC:
1.6.5 (Build 27624) (July 25, 2012 (2012-07-25)) [3][5]

3.11 (October 23, 2015 (2015-10-23)) [6][7]
Preview release

3.3 (Server; build 30470) (April 3, 2014 (2014-04-03)) [8]
Microsoft Windows
3.4.6 (Beta; build 41288) (October 27, 2015 (2015-10-27)) [9]

1.8.8 (Beta; build 40618) [10]
Development status Active
Written in C++[11]
Operating system Android (2.1 and later),[6] Linux (officially supported using Wine;[12] native server version also available[13]), Microsoft Windows, OS X (10.5; Intel and PPC)
Size 8.69 MB (Android)
2.09-2.23 MB (Linux)
1.66 MB (Microsoft Windows)
1.29 MB (OS X)
Available in 67 languages
Type BitTorrent client
License Adware
Website .com.utorrentwww

µTorrent, or uTorrent (see pronunciation) is a freeware, ad-supported, proprietary BitTorrent client owned and developed by BitTorrent, Inc. With over 100 million users[14] it is the most widely used BitTorrent client outside China; globally only behind Xunlei.[15] The "µ" (Greek letter "mu") in its name comes from the SI prefix "micro-", referring to the program's small memory footprint: the program was designed to use minimal computer resources while offering functionality comparable to larger BitTorrent clients such as Vuze or BitComet. The program has received consistently good reviews for its feature set, performance, stability, and support for older hardware and versions of Windows.

The program has been in active development since its first release in 2005. Although originally developed by Ludvig Strigeus, since December 7, 2006, the code is owned and maintained by BitTorrent, Inc.[16] The code has also been employed by BitTorrent, Inc. as the basis for version 6.0 and above of the BitTorrent client, a re-branded version of µTorrent. All versions are written in C++.[11]


  • History 1
    • Early development 1.1
    • PeerFactor SARL 1.2
    • Ownership change 1.3
  • Features 2
    • Size 2.1
    • Operating system support 2.2
  • Revenue 3
    • Toolbars 3.1
    • Paid version 3.2
    • Ads and malware 3.3
  • Pronunciation 4
  • Contributors 5
  • Reception 6
  • Languages 7
  • See also 8
  • References 9
  • External links 10


Early development

Out of general discontent with bloatware, Serge Paquet suggested to Ludvig Strigeus that he should make a smaller and more 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 last quarter of 2004 (the first build is dated October 17, 2004), mostly during his free time before and 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.

PeerFactor SARL

On March 4, 2006, PeerFactor SARL announced the signing of a six-month contract with Strigeus for the development of "new content distribution applications on the Web."[17] 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.[18] At the time there was some speculation that μTorrent may have been modified to spy on users on Peerfactor's behalf,[17][19] 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.[16]

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).


Features present in µTorrent include:

  • Magnet Links (URIs), added in version 1.8, released on August 9, 2008.[20]
  • Teredo tunneling / IPv6 support
  • Micro Transport Protocol (µTP) preliminary support as of 1.8.2 with full-support added in 2.0
  • UPnP support for all versions of Windows, without needing Windows XP's UPnP framework
  • Protocol encryption (PE)
  • Peer exchange (PEX) with other BitTorrent clients:
    • libtorrent and clients based on it like Deluge or qBittorrent 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
    • Vuze, formerly Azureus, has full support as of version
  • 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 67 languages.[21]
  • Initial seeding of torrents
  • Customizable search bar & user interface design.[22]
  • 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 browser
    • A new web user interface, codenamed Falcon, is in development. It supports encrypted sessions and the ability of going through firewalls without port forwarding, while being more complete and easier to start using than its predecessor.[23]
  • 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.[24]
  • Quick-resumes interrupted transfers
  • Versions of µTorrent up to 1.8.5 build 17091[25] can use as little as 14 MB of RAM running on a 486 processor on Windows 95.[26]
  • Two "easter egg" hidden features in the About subsection of Help: clicking the µTorrent logo plays a Deep Note-like sound effect,[27] and typing the letter "t" starts a Tetris-like game called μTris,[27][28][29] which in 2008 was selected as #1 of the "Top 10 Software Easter Eggs" by LifeHacker.[30]


µTorrent is shipped as a single stand-alone compressed executable file, installed at first run. 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.

Operating system support

Screenshot of the Mac OS X version of μTorrent (up to 0.9.2)
Screenshot of μTorrent Server viewed in Firefox

µTorrent is available for Microsoft Windows, Mac OS X, and Android.[6][31] A µTorrent Server is also available for Linux.[13]

The first test version for Mac OS X, running on Mac OS X 10.5, was released on 27 November 2008.[32]

On September 2, 2010, the native Linux version of µTorrent Server was released. Firon, an administrator of the µTorrent community forum, said that they had been working on this project for a few months prior to the release as it was the most requested feature for some time. This release is intended for users who are seeking a fast command-line interface based BitTorrent client with a remote web-based management. They also mentioned that a full featured client with a GUI is a work in progress.[33] He also said: "This is a native Linux port and is known to work on Ubuntu 9.10+, Debian 5+ and Fedora 12+. Others may work, but they are not officially supported. Kernel 2.6.13 or newer required. 64-bit host systems currently have some problems, so 32-bit only for now. For trackers who whitelist, the user agent is "uTorrent/300B(build#)(server)". The peerid is identical to the Windows 3.0 client. They share version numbers because of a common codebase."[33]

Currently μTorrent supports Windows XP or newer and Mac OS X 10.5 or newer.[31]


In early versions, Strigeus had built in a web redirection via nanotorrent for search queries entered through the search bar that displayed advertisements in a frame on the web browser. Some users thought this suspicious because tracking could be implemented by recording the IP addresses of those downloading/receiving the advertisements, and the search functionality could easily be used to track user queries through whichever web-interface the client is going through to execute the search. After a short trial period, the advertising was disabled, mitigating possible concerns.[34]

A later version of the software has, instead of ads, a "search all sites" feature, which is a keyword-based search bar that delivers listings of torrent files at different trackers. A frame at the top displays advertisements (server-side) in the browser when the search function is used. In version 1.5, no ads are present in the program itself.

As of build 463, a redirect bypass feature became available in the Advanced options.

As of version 1.8.2, the µTorrent installer gives the user the option to download and install the toolbar. This is done on the first run of the program and the user may explicitly opt out of this feature by deselecting it.[35][36] The developers stated the addition was needed for funds to continue development. In late 2010, this was replaced with the Conduit Engine.


In late 2010, some controversy arose with a release of µTorrent which included adware in the form of the Conduit Engine, which installed a toolbar, and made homepage and default search engine changes to a user's web browser. A number of users reported that the installation was made without the user's consent.[37] There were some complaints that the adware software was difficult to remove.[38] In 2011, µTorrent bundled the Bing Toolbar.[39]

On July 15, 2011, BitTorrent announced that they would offer a paid version of µTorrent called "µTorrent Plus". This new version would offer extra features, such as integrated file conversion, anti-virus and a built in media player.[40] On 6 October 2011, the Pre-alpha of µTorrent Plus was released to an invitation only community.[41] As of December 2011, µTorrentPlus 3.1 was available for $24.95; as of December 2014, the Plus version was available as a $19.95 yearly subscription.

Ads and malware

In August 2012, BitTorrent announced the addition of advertising in the free version of µTorrent which could be individually dismissed by users.[42] Due to response from users, a few days later, the company stated that ads could be optionally turned off.[43] A user-created tool known as "Pimp My µTorrent" was also created to simplify the process of disabling ads in the Windows version.[44] Starting with µTorrent version 3.2.2, the software also contains in-content advertisements described as "Featured Torrent".[45] As with ads, it is possible to disable this content.[45]

In March 2015, it was alleged that µTorrent had automatically installed a program known as Epic Scale—a program classified as "riskware" by some security programs, which mines the cryptocurrency Litecoin in the background for BitTorrent, Inc. (allegedly giving a portion to charity), utilizing CPU and GPU power. A µTorrent developer disputed the claim that it was automatically installed, and claimed that as with all other "partner" programs bundled with the software, users could decline the installation.[46][47][48] On 28 March, Epic Scale was permanently removed from the installation and as a software bundle partner.[49]


The author of µTorrent wrote in 2005, "I usually say 'you torrent' because it looks like a u", and offered "microtorrent", "mytorrent" (as "my" [myː] is the Swedish pronunciation of the Greek letter µ) and later "mutorrent" as alternate pronunciations.[50]

The symbol μ is the lowercase Greek letter mu, which stands for the SI prefix "micro-" meaning "one millionth". It refers to the program's small footprint.


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 Adam Kelly[51] ("AdamK"), Arvid Norberg ("arvid", author of libtorrent), among others at BitTorrent Inc. Strigeus is no longer affiliated.


μTorrent was once praised for its small size and minimal computer resources used, which set it apart from other clients. PC Magazine stated that it "packs an outstanding array of features" in 2006[52] and listed it in their 2008 "Best free 157 software tools".[53] It was also in PC World's "101 Fantastic freebies".[54] The website said it was the most feature rich BitTorrent client available,[55] later summarizing a 2009 University of California, Riverside study[56] which concluded that "µTorrent Download Speeds Beat Vuze By 16%" on average and "on 10% of [the 30 most used] ISPs, µTorrent users were downloading 30% faster than Vuze users".[57] said it was the best BitTorrent client available, citing its small size and "minimal impact to the rest of your computer's speed."[58] said its "memory footprint is also ridiculously small".[59] PC & Tech Authority magazine (Australia) gave it 6 stars (out of 6).[60] rated it the best BitTorrent client available (Windows) in 2008[61] and 2011 (Windows[62] and Mac[63]). gave it 5 stars (of 5) saying it features "light and quick downloading".[64]

In November 2009, 52 million users were reported to be using the application,[65] and in late 2011, 132 million.[66]

According to a study by Arbor Networks, the 2008 adoption of IPv6 by µTorrent caused a 15-fold increase in IPv6 traffic across the Internet over a ten-month period.[67]


The software is available in over 65 languages.

See also


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  10. ^
  11. ^ a b
  12. ^
  13. ^ a b
  14. ^ Spotify Reminded of uTorrent past after branding Grooveshark "pirates". TorrentFreak. November 12, 2014.
  15. ^
  16. ^ a b
  17. ^ a b
  18. ^
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  20. ^
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  26. ^ a b
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  30. ^ a b
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  32. ^ a b
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  38. ^ Translation
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  44. ^ a b
  45. ^
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  48. ^
  49. ^
  50. ^
  51. ^
  52. ^ "The Best Free Software 2008 - 157 software tools". PC Magazine. February 8, 2008.
  53. ^ "101 Fantastic freebies". PC World. 2007-03-28.
  54. ^
  55. ^
  56. ^
  57. ^
  58. ^
  59. ^
  60. ^
  61. ^ Gordon, Whitson (November 1, 2011). "The Best Bittorrent Client for Windows". Retrieved 2013-02-05.
  62. ^ Dachis, Adam (October 31, 2011). "The Best BitTorrent Client for Mac". Retrieved 2013-02-05.
  63. ^
  64. ^ "µTorrent Users Double to 52 Million in a Year". TorrentFreak. 2009-12-25. Retrieved on 2010-11-09.
  65. ^ O'Flaherty, Kate (January 10, 2012). "Bit Torrent user numbers rise to 150 million per month". The Inquirer (UK). Retrieved 2013-02-05.
  66. ^ Leyden, John (2009-09-10). "P2P pushes IPv6 surge". The Register (UK). Retrieved 2013-02-05.

External links

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