Main article: History of YouTube
Domain name problem
YouTube's immense success unintentionally affected the business of an American company, Universal Tube & Rollform Equipment Corp., whose original website address, utube.com, was at one time frequently overloaded and shut down by high numbers of visitors unsure about the spelling of YouTube's domain name. At the beginning of November 2006, Universal Tube filed suit in federal court against YouTube, requesting that the youtube.com domain be transferred to them. As of May 2008, the web address utube.com is inactive, while Universal Tube & Rollform Equipment has moved to utubeonline.com. According to a WHOIS domain name search, Universal Tube still owns the domain http://www.utube.com.
Main article: Social impact of YouTube
The guitar video of Pachelbel's Canon is one of the most popular music videos on YouTubeBefore the launch of YouTube in 2005, there were few simple methods available for ordinary computer users who wanted to post videos online. With its easy to use interface, YouTube made it possible for anyone who could use a computer to post a video that millions of people could watch within a few minutes. The wide range of topics covered by YouTube has turned video sharing into one of the most important parts of Internet culture.
An early example of the social impact of YouTube was the success of the Bus Uncle video in 2006. It shows an animated conversation between a youth and an older man on a bus in Hong Kong, and was discussed widely in the mainstream media. Another YouTube video to receive extensive coverage is guitar, which features a performance of Pachelbel's Canon on an electric guitar. The name of the performer is not given in the video, and after it received millions of views the New York Times revealed the identity of the guitarist as Jeong-Hyun Lim, a 23-year-old from South Korea who had recorded the track in his bedroom. 
Terms of service
According YouTube's terms of service, users may upload videos only with permission of the copyright holder and people depicted in the videos. Pornography, nudity, defamation, harassment, commercial advertisements and material encouraging criminal conduct are prohibited. The uploader grants YouTube a license to distribute and modify the uploaded material for any purpose; this license terminates when the uploader deletes the material from the site. Users may view videos on the site as long as they agree to the terms of service; downloading through one's own means or copying of the videos is not permitted.
Further information: Censorship by Google#YouTube
Main article: Criticism of YouTube
Example of a copyrighted YouTube video claimed by Red De Television, ChileVision SA.YouTube has been criticized frequently for failing to ensure that its online content adheres to the law of copyright. At the time of uploading a video, YouTube users are shown a screen with the following message:
Do not upload any TV shows, music videos, music concerts or commercials without permission unless they consist entirely of content you created yourself. The Copyright Tips page and the Community Guidelines can help you determine whether your video infringes someone else's copyright.
Despite this advice, there are still many unauthorized clips from television shows, films and music videos on YouTube. YouTube does not view videos before they are posted online, and it is left to copyright holders to issue a takedown notice under the terms of the Digital Millenium Copyright Act. Organizations including Viacom and the English Premier League have issued lawsuits against YouTube, claiming that it has done too little to prevent the uploading of copyrighted material. Viacom, demanding $1 billion in damages, said that it had found more than 150,000 unauthorized clips of its material on YouTube that had been viewed "an astounding 1.5 billion times". YouTube responded by stating that it "goes far beyond its legal obligations in assisting content owners to protect their works". Since Viacom issued its lawsuit, YouTube has introduced a system of digital fingerprints that checks uploaded videos against the original content as a means of reducing copyright violation.
YouTube has also faced criticism over the offensive content in some of its videos. Although YouTube's terms of service forbid the uploading of material likely to be considered inappropriate or defamatory, the inability to check all videos before they go online means that occasional lapses are inevitable. Controversial areas for videos have included Holocaust denial and the Hillsborough Disaster, in which 96 football fans from Liverpool were crushed to death in 1989.
Main article: Blocking of YouTube
YouTube has been blocked in several countries since its inception, including Tunisia, Thailand (which has since been lifted) and Iran. Certain video pages were banned as of October 1, 2007 in Turkey, but this was lifted two days later. More recently on January 22, 2008 Turkey banned YouTube once again but this ban was lifted after three days. Certain pages are also banned in United Arab Emirates.
On February 23, 2008, Pakistan blocked YouTube due to "offensive material" towards the Islamic faith, including the display of pictures of the prophet Muhammad. This action by the Pakistani authorities led to a near global blackout of the YouTube site for at least two hours. Thousands of Pakistanis undermined the 3-day block using a VPN software called Hotspot Shield. The YouTube ban was lifted on February 26, 2008 after the "offensive material" were removed from the site.
Schools in certain countries have begun to block access to YouTube due to students uploading videos of bullying behavior, school fights and racist behavior as well as increased bandwidth usage and other inappropriate content.
Main article: Spam targeting video sharing sites
With recent improvements to e-mail spam filtering technology and their wider use, spammers have begun using YouTube as way to advertise: popular videos frequently have comments with links to irrelevant external sites, usually with some enticing statements (such as "Great video, go to
“ The messages came from email@example.com. [...] The messages look like a legitimate YouTube invite, except they include typical spam content like stock pump-and-dump promotions and links to spam Web sites. Many of them use Microsoft's recent XBox 360 hit "Halo 3" as bait, telling the recipient they have won a free copy of the game and to go to a Web site. If they take the bait and click on "winhalo3.com," the Web site infects them with the Storm Worm, which has been hanging around since August. ”
Spammers have used this route more often nowadays because they can use it to defeat spam filters, gain more readers and possibly customers. "They just do as all spammers do..."
Uploading Video on YouTubeAs of November 2007 YouTube plays back videos limited in both size and quality. The size is limited to pixel dimensions of 320 by 240 and the quality is limited to a bitrate of around 314 kbit/s with a frame rate dependent on the uploaded video. YouTube limits the playback size and quality by re-encoding the user's uploaded video at the time of upload. In 2006 YouTube permitted playback at higher quality, larger sizes, and in stereo, but some time after January 2007 YouTube applied quality reductions to new uploads.
YouTube's video playback technology is based on Macromedia's Flash Player 9 and uses the Sorenson Spark H.263 video codec. This technology allows the site to display videos with quality comparable to more established video playback technologies (such as Windows Media Player, QuickTime and RealPlayer) that generally require the user to download and install a web browser plugin in order to view video. Flash also requires a plug-in, but Adobe considers the Flash 7 plug-in to be present on about 90% of online computers. The video can also be played back with third-party media players such as GOM Player, gnash, VLC as well as some ffmpeg-based video players.
Videos uploaded to YouTube are limited to ten minutes in length, and a file size of 1024MB (1 Gigabyte). One video at a time can be uploaded through the standard interface, and multiple videos can be uploaded with a Windows based plugin.  YouTube converts videos into the Flash Video format after uploading. YouTube also converts content to other formats so that it can be viewed outside of the website. See below.
YouTube accepts uploaded videos in the .WMV, .AVI, .MOV, MPEG and .MP4 formats. It also supports 3GP, allowing videos to be uploaded directly from a mobile phone.
Users can view videos in windowed mode or full screen mode and it is possible to switch modes during playback without reloading it due to the full-screen function of Adobe Flash Player 9.
On September 14, 2007, Members of the VIDEOHelp.com forums discovered a method to allow high-quality video and stereo sound. The method involved converting a video to the .flv format YouTube uses, and using a Hex Editor to extend the video's displayed playback time (usually to 10 or 11 minutes for non-Director accounts), thus "tricking" YouTube into believing that the file's bitrate was much lower than it actually was. Although load times significantly increased for videos, both video and sound quality was notably better than in comparable videos uploaded without the method. However, on February 4, 2008, following a maintenance period, YouTube took countermeasures against this method, and it is now impossible to upload high-quality videos. This had no effect on any high-quality videos already uploaded to YouTube.
High Quality videos
Comparison of high and standard quality YouTube videos (480x360 and 320x240 pixels)In March 2008, YouTube launched 'High Quality' versions of its videos. The new version offers the possibility of better video definition (480x360 pixels instead of the standard 320x240 pixels) for any video uploaded after this date. YouTube will decide which videos are capable of this improved quality based on the standard of the original upload. Users can choose "always show me higher quality when available" on their video quality settings page in their Account pages to switch automatically to the better quality.
Asked why YouTube did not choose HD format, the site answered : "Our general philosophy is to make sure that as many people as possible can access YouTube and that videos start quickly and play smoothly. That's one reason why you don't see us racing to call this "Super Duper YouTube HD," because most people don't want to wait a long time for videos to play."
YouTube files contain an MP3 audio stream. By default, it is encoded in mono at a bit rate of 64 kbit/s sampled at 22050 Hz, giving an audio bandwidth of around 10 kHz. The default bit rate delivers passable but not hi-fi audio quality. It is possible for a YouTube video to have a stereo audio track if the movie file is converted to FLV format prior to upload. This can be done with programs including ffmpeg for Linux and Windows, ffmpegX for Macintosh or the commercial Riva FLV Encoder for Windows.
As noted above, YouTube accepts common file formats and converts them to the H.263 variant of Flash Video, and makes them available for online viewing. Beginning in June 2007, newly uploaded videos will also be encoded using the H.264 video standard (basically an improved form) to enable streaming of YouTube videos on the Apple TV, iPhone, and iPod touch.
On Apple TV
Apple Inc. announced on 20 June 2007 that YouTube is accessible on the Apple TV after installation of a free software update. Functionality includes browsing by category, searching videos, and the ability for members to log onto their YouTube accounts directly on Apple TV. Access to thousands of the most current and popular YouTube videos are available, and there were plans to add thousands more videos each week. The entire catalog was targeted to be available in fall 2007. According to Apple VP David Moody, the reason for the delay was the need for all current YouTube content to be transcoded to Apple's preferred video standard, H.264. All content uploaded in and after June, however, was and will be automatically encoded into H.264, rendering additional transcoding unnecessary for these newer files.
YouTube launched its mobile site, YouTube Mobile on 15 June 2007. It is based on xHTML and uses 3GP videos with H263/AMR codec and RTSP streaming. It is available via a web interface at m.youtube.com or via YouTube's Mobile Java Application.
YouTube TV Channel is on Information TV 2, and it started January 7, 2008. The channel is airing video sharing content from the YouTube website.
On iPhone and iPod touch
Apple announced Wednesday, 20 June 2007 that YouTube would be available on iPhone at launch. Streaming is over WiFi or EDGE.
Videos on YouTube for the iPhone are encoded in Apple's preferred H.264 format. All videos are viewed in the horizontal orientation of the phone. As YouTube videos have 4:3 aspect ratio and the iPhone is 3:2, videos must be viewed with black bars on the side (pillarboxed) or may be zoomed to trim some of the top and bottom to fill the screen.
Not all videos were available on iPhone initially because not every video was reencoded to H.264. There are two versions of each video on YouTube, one is higher bandwidth for WiFi use, and one is lower resolution for EDGE use.
Unlike the Apple TV version, users cannot log in to their own YouTube accounts, but can create a separate favorites list just for the iPhone.
Each video is accompanied by the full HTML markup for linking to it and/or embedding it within another page, unless the submitter of a video chooses to disable the embedding feature. A small addition to the embeddable markup will allow the video to play automatically when the webpage loads. These simple cut-and-paste options are especially popular with users of social-networking sites. Poor experiences, however, have been cited by users of such sites, where autoplaying embedded YouTube videos has been reported to slow down page loading time or even to crash internet browsers.
The YouTube Player is the name of another embeddable applet (with a different interface), designed for browsing YouTube videos on an iGoogle homepage.
YouTube itself does not make it easy to download and save videos for offline viewing or editing (in fact, YouTube's official FAQ even states that "you can't download our videos to your computer") nor for viewing in external players, but several third-party web sites, applications, browser extensions (such as Firefox extensions) exist for that purpose. Further there are also several online (server based) services. Alternatively, most .flv files can be copied from the 'Temporary Internet Files' folder in Windows, or the /tmp directory in GNU systems, to a permanent folder. The .flv files can then be viewed and edited directly or converted to other formats using various applications such as VLC media player.
In June 2008, YouTube launched a beta test of Annotations, which can display notes or links within a video. Annotations allow for information to be added, for example stories with multiple possibilities (viewers click to choose the next scene), and links to other YouTube videos. Annotations are currently available only on the English language YouTube and will not appear on videos embedded outside the YouTube website.