Most modern smartphones can access YouTube videos either in the app or through an optimized website. YouTube Mobile started in June 2007 with RTSP video streaming. Not all YouTube videos are available on the mobile version of the site. Since June 2007, YouTube videos have been released for display on a range of Apple products. This requires the YouTube content to be encoded according to H.264, Apple’s preferred video standard. This process took several months. YouTube videos can be watched on devices like Apple TV, iPod Touch and iPhone. In July 2010, the mobile version of the website was rebooted based on HTML5, eliminating the need for Adobe Flash Player and optimizing its use with touchscreen controls. A mobile version is also available as an application for the Android platform. In September 2012, YouTube launched its first iPhone application after it decided to remove YouTube as one of the preloaded applications on the iPhone 5 and iOS 6. According to GlobalWebIndex, YouTube used 35% of smartphone users between April and June 2013, making it the third most used application.
The update of the TiVo service in July 2008 enabled the system to search and play videos on YouTube. In January 2009, YouTube launches YouTube for Television, multimedia TVs with web browsers, and is now available for free on the PlayStation 3 and Wii game consoles. In June 2009, YouTube introduced XL, which offers a simplified interface for viewing on a standard television screen. YouTube is also available as an Xbox Live app. On November 15, 2012, Google launches the official Wii app, which allows users to watch YouTube videos over the Wii channel. The Wii U and Nintendo 3DS application can also be viewed in the Wii U Internet browser with HTML5. Google provided Roku YouTube on December 17, 2013, and in October 2014, the Sony PlayStation 4.
YouTube conducted early experiments with live broadcasts, including a U2 concert in 2009 and a question and answer with US President Barack Obama in February 2010. These tests were conducted in September 2010 and YouTube began testing its own streaming infrastructure. In April 2011, YouTube announced the launch of YouTube Live with a portal page at www.youtube.com/live. The creation of live streams was initially limited to selected partners. It was used to broadcast real-time events like the 2012 London Olympics. In October 2012, more than 8 million people saw Felix Baumgartner jump from the edge of space as a live broadcast on YouTube.
In May 2013, the creation of live broadcasts for verified users with at least 1000 subscribers was started. In August of the same year, the number was reduced to 100 subscribers and in December, the limit was lifted. Initially, live broadcast over mobile was initially restricted to users with at least 10,000 subscribers, but reduced to 100 subscribers by mid-2017. Direct streams can be up to 4K at a resolution of 60 frames per second. Therefore, 360 ° videos are supported. In February 2017, a streaming feature called Super Chat was introduced that allows viewers to donate between $ 1- $ 500 to highlight their comments
Initially, YouTube only offered videos with a quality level displayed at a resolution of 320 × 240 pixels, using the Sorenson Spark codec (option H.263), with mono MP3 audio. In June 2007, YouTube added the ability to view 3GP videos on mobile phones.  In March 2008, a high-quality mode was added that increased the resolution to 480 × 360 pixels. In November 2008, support for 720p HD was added. When the 720p player was launched, YouTube changed from 4: 3 to 16: 9 widescreen.  With this new feature, YouTube started switching to H.264 / MPEG-4 AVC as the standard video compression format. In November 2009, support for 1080p HD was added. In July 2010, YouTube announced that it has released a series of 4K videos that allow it to resolve up to 4096 × 3072 pixels. In June 2015, support for 8K resolution was added, and the video was played at a resolution of 7680 × 4320 pixels. In November 2016 support was added for HDR video that can be encoded with Hybrid Log Gamma (HLG) or Perceptual Quantizer (PQ). HDR video can be encoded with Rec. 2020.
In June 2014, videos at 60 frames per second appeared on YouTube to play video games at a frame rate comparable to high-performance video cards. Videos are played at a resolution of 720p or higher. YouTube videos are available in different quality levels. Previous Standard Quality (SQ), High Quality (HQ), and High Definition (HD) titles have been replaced by numeric values representing the vertical resolution of the video. The streaming video stream is encoded in VP9 format with opus stereo sound. If VP9 / WebM is not supported in a browser / device or in Windows XP user agent reports, AVC H.264 / MPEG-4 video with AAC stereo sound will be used instead.
All YouTube users can upload videos of up to 15 minutes each. You may have been able to download more videos, but it was a 10-minute show and movie. The 10-minute limit was increased to 15 minutes in July 2010. The videos have been uploaded more than 12 hours in the past. Video size can be up to 128 GB.  Video titles are created when loaded using speech recognition technology. For greater accuracy.
YouTube accepts videos that are downloaded in most container formats, including AVI, MP4, MPEG-PS, QuickTime file format, and FLV. It supports WebM and 3GP files,
For progressive scan or interlaced video, you cannot see what you downloaded. Use progressive scan. This is not a sign that it is really shrinking. YouTube attributes this to downloading content created for television.