μTorrent, or uTorrent (see pronunciation) is a proprietary adware BitTorrent client owned and developed by BitTorrent, Inc. With over 150 million users it is the most widely used BitTorrent client outside China; globally only behind Xunlei. 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. μTorrent became controversial in 2015 when many users unknowingly accepted a default option during installation which also installed a cryptocurrency miner. The miner was removed in later versions, but had already done irreversible damage to μTorrent's reputation.
|Original author(s)||Ludvig Strigeus|
|Initial release||September 18, 2005|
|Stable release||3.5.5 (build 46036) (30 June 2021 ) [±]|
|Preview release||3.5.5 Beta (build 46016) (12 May 2021 ) [±]|
|Operating system||Android, Linux (Server version only, only officially supports very old versions of Debian and Ubuntu), Microsoft Windows, macOS|
|Available in||English, Albanian, Arabic, Belarusian, Brazilian, Bengali, Bulgarian, Chinese, Czech, Dutch, Finnish, French, German, Hebrew, Hindi, Hungarian, Italian, Japanese, Korean (Default), Persian, Polish, Portuguese, Romanian, Russian, Spanish, Swedish, Thai, Turkish, Ukrainian and Vietnamese|
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. 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++.
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 free software, and began generating feedback.
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." 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. At the time there was some speculation that μTorrent may have been modified to spy on users on Peerfactor's behalf, however to date (even following μTorrent's acquisition by BitTorrent, Inc.) no evidence has been produced to support these allegations.
On September 18, 2007, BitTorrent 6.0 was released. Although previous versions of the BitTorrent client had been open source software, with version 6 it became proprietary.
In April 2017, BitTorrent founder Bram Cohen announced that the next version of μTorrent would be web browser based. This μTorrent version allows users to stream torrents from the default web browser, similar to a regular streaming site.
Features present in μTorrent include:
- Magnet Links (URIs), added in version 1.8, released on August 9, 2008.
- 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 22.214.171.124
- 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.
- Initial seeding of torrents
- Customizable search bar & user interface design.
- 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
- 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.
- Quick-resumes interrupted transfers
- Versions of μTorrent up to 1.8.5 build 17091 can use as little as 14 MB of RAM running on a 486 processor on Windows 95.
- Two "easter egg" hidden features in the About subsection of Help: clicking the μTorrent logo plays a Deep Note-like sound effect, and typing the letter "t" starts a Tetris-like game called μTris, which in 2008 was selected as #1 of the "Top 10 Software Easter Eggs" by LifeHacker.
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
The first test version for macOS, running on Mac OS X Leopard, was released on 27 November 2008.
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. 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.
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.
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 Ask.com toolbar. This is done on the first run of the program and the user may explicitly opt out of this feature by deselecting it. 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. There were some complaints that the adware software was difficult to remove. In 2011, μTorrent bundled the Bing Toolbar.
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. On 6 October 2011, the Pre-alpha of μTorrent Plus was released to an invitation only community. 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. Due to response from users, a few days later, the company stated that ads could be optionally turned off. A user-created tool known as "Pimp My µTorrent" was also created to simplify the process of disabling ads in the Windows version. Starting with µTorrent version 3.2.2, the software also contains in-content advertisements described as "Featured Torrent". As with ads, it is possible to disable this content.
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. On 28 March, Epic Scale was permanently removed from the installation and as a software bundle partner.
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 alternative pronunciations. In Greece, where the software is widely used, it is called 'me torrent', since the letter μ of the Greek Alphabet is pronounced [mi] in modern Greek. The symbol μ is the lowercase Greek letter mu, which stands for the SI prefix "micro-". It refers to the program's originally 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 macOS ports. He maintained the μTorrent website and forum up until the end of 2005, but is no longer affiliated with μTorrent.
Since its purchase in 2006, development has been performed by various employees of Bittorrent Inc. Strigeus is no longer affiliated.
μTorrent has been 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 and listed it in their 2008 "Best free 157 software tools". It was also in PC World's "101 Fantastic freebies". The website TorrentFreak.com said it was the most feature rich BitTorrent client available, later summarizing a 2009 University of California, Riverside study 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". About.com said it was the best BitTorrent client available, citing its small size and "minimal impact to the rest of your computer's speed." Wired.com said its "memory footprint is also ridiculously small". PC & Tech Authority magazine (Australia) gave it 6 stars (out of 6). Lifehacker.com rated it the best BitTorrent client available (Windows) in 2008, 2011 (Windows and Mac) and a follow-up user poll rated it the most popular torrent client in 2015. CNET.com gave it 5 stars (of 5) saying it features "light and quick downloading".
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.
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Solving math problems for weather prediction, physics simulations, cryptography (including cryptocurrency mining) and more has real world value. We solve these problems on behalf of our trusted partners, and donate proceeds to your favorite charities.
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- Official website
- μTorrent on Google Play
- uTorrent: A Beginner's Guide to BitTorrent Downloading by Jared M
- p2pnet uTorrent interview by Alex H
- Can great software live in 130 kilobytes? by George Ou
- Glasnost test BitTorrent traffic shaping (Max Planck Institute for Software Systems)