All YouTube users can upload videos up to 15 minutes each in duration. Users can verify their account, normally through a mobile phone, to gain the ability to upload videos up to 12 hours in length, as well as produce live streams.[108][109] When YouTube was launched in 2005, it was possible to upload longer videos, but a 10-minute limit was introduced in March 2006 after YouTube found that the majority of videos exceeding this length were unauthorized uploads of television shows and films.[110] The 10-minute limit was increased to 15 minutes in July 2010.[111] Videos can be at most 256 GB in size or 12 hours, whichever is less.[108] As of 2021, automatic closed captions using speech recognition technology when a video is uploaded is available in 13 languages, and can be machine-translated during playback.[112]
YouTube also offers manual closed captioning as part of its creator studio.[113] YouTube formerly offered a 'Community Captions' feature, where viewers could write and submit captions for public display upon approval by the video uploader, but this was deprecated in September 2020.[114]
YouTube accepts the most common container formats, including MP4, Matroska, FLV, AVI, WebM, 3GP, MPEG-PS, and the QuickTime File Format. Some intermediate video formats (i.e., primarily used for professional video editing, not for final delivery or storage) are also accepted, such as ProRes.[115] YouTube provides recommended encoding settings.[116]
Each video is identified by an eleven-character case-sensitive alphanumerical Base64 string in the Uniform Resource Locator (URL) which can contain letters, digits, an underscore (_), and a dash (-).[117]
In 2018, YouTube added a feature called Premiere which displays a notification to the user mentioning when the video will be available for the first time, like for a live stream but with a prerecorded video. When the scheduled time arrives, the video is aired as a live broadcast with a two-minute countdown. Optionally, a premiere can be initiated immediately.[118]YouTube primarily uses the VP9 and H.264/MPEG-4 AVC video codecs, and the Dynamic Adaptive Streaming over HTTP protocol.[94] MPEG-4 Part 2 streams contained within 3GP containers are also provided for low bandwidth connections.[95] By January 2019, YouTube had begun rolling out videos in AV1 format.[96] In 2021 it was reported that the company was considering requiring AV1 in streaming hardware in order to decrease bandwidth and increase quality.[97] Video is usually streamed alongside the Opus and AAC audio codecs.[95]
At launch in 2005, viewing YouTube videos on a personal computer required the Adobe Flash Player plug-in to be installed in the browser.[98] In January 2010, YouTube launched an experimental version of the site that used the built-in multimedia capabilities of web browsers supporting the HTML5 standard.[99] This allowed videos to be viewed without requiring Adobe Flash Player or any other plug-in to be installed.[100] On January 27, 2015, YouTube announced that HTML5 would be the default playback method on supported browsers.[99] With the switch to HTML5 video streams using Dynamic Adaptive Streaming over HTTP (MPEG-DASH), an HTTP-based adaptive bit-rate streaming solution optimizes the bitrate and quality for the available network.[101]
The platform can serve videos at optionally lower resolution levels starting at 144p for smoothening playback in areas and countries with limited Internet speeds, improving compatibility, as well as for the preservation of limited cellular data plans. The resolution setting can be adjusted automatically based on detected connection speed, as well as be set manually.[102][103]
From 2008 to 2017, users could add "annotations" to their videos—such as pop-up text messages and hyperlinks, which allowed for interactive videos. By 2019 all annotations had been removed from videos, breaking some videos which depended on the feature. YouTube introduced standardized widgets intended to replace annotations in a cross-platform manner, including "end screens" (a customizable array of thumbnails for specified videos displayed near the end of the video).[104][105][106]
In 2018, YouTube became an ISNI registry, and announced its intention to begin creating ISNI identifiers to uniquely identify the musicians whose videos it features.[107] In 2020 it launched video chapters as a way to structure videos and improve navigation.
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