Get Youtube information via JSON for single video (not feed) in Javascript

UPDATED 2018

API v2 deprecated. New youtube api v3 works only with developer token and has limitation for free connections.

You can get JSON without API:

http://www.youtube.com/oembed?url=http://www.youtube.com/watch?v=ojCkgU5XGdg&format=json

Or xml

http://www.youtube.com/oembed?url=http://www.youtube.com/watch?v=ojCkgU5XGdg&format=xml

new 2018 json response has

{
  "html": "<iframe width=\"480\" height=\"270\" src=\"https://www.youtube.com/embed/ojCkgU5XGdg?feature=oembed\" frameborder=\"0\" allow=\"autoplay; encrypted-media\" allowfullscreen></iframe>",
  "title": "Creativity and Drugs (Eng Sub)",
  "thumbnail_height": 360,
  "provider_name": "YouTube",
  "author_url": "https://www.youtube.com/user/serebniti",
  "thumbnail_width": 480,
  "height": 270,
  "provider_url": "https://www.youtube.com/",
  "type": "video",
  "width": 480,
  "version": "1.0",
  "author_name": "serebniti",
  "thumbnail_url": "https://i.ytimg.com/vi/ojCkgU5XGdg/hqdefault.jpg"
}

Thumbs:

hqdefault.jpg has less quality but always exist.

http://img.youtube.com/vi/ojCkgU5XGdg/hqdefault.jpg

http://img.youtube.com/vi/ojCkgU5XGdg/sddefault.jpg

Max size

https://i.ytimg.com/vi/ojCkgU5XGdg/maxresdefault.jpg

Mini thumbs:

http://img.youtube.com/vi/ojCkgU5XGdg/0.jpg
http://img.youtube.com/vi/ojCkgU5XGdg/1.jpg
http://img.youtube.com/vi/ojCkgU5XGdg/2.jpg
http://img.youtube.com/vi/ojCkgU5XGdg/3.jpg

Annotations

http://www.youtube.com/annotations_invideo?cap_hist=1&video_id=ojCkgU5XGdg

parse mobile page 16kb

https://m.youtube.com/watch?v=ojCkgU5XGdg

don’t forget change user agent to iOS / Safari 7

also

http://www.youtube.com/get_video_info?html5=1&video_id=ojCkgU5XGdg

also how embed youtube live

https://www.youtube.com/embed/live_stream?channel=UCkA21M22vGK9GtAvq3DvSlA

Where UCkA21M22vGK9GtAvq3DvSlA is your channel id.
You can find it inside youtube account on “My Channel” link.

Live thumb

https://i.ytimg.com/vi/W-fSCPrYSL8/hqdefault_live.jpg