YouTube

1st logo 2005–2011(Codename:Polar Bowler)
The logo consists of a black "You" and a red rounded rectangle with the word "Tube" in it. It can also contain the "Broadcast Yourself" tagline underneath. It was originally scheduled to be released in 2003, but was delayed until 2005. As of 2011, this is now being used as a secondary logo.

2nd logo 2011–2013(Codename:Caidin 2011 Era Logo)
This modification of the YouTube logo was introduced in July 2011 as a part of the Cosmic Panda experiment. It officially became the new logo a few months later. With the introduction of the entirely new layout on December 6, 2012, the slogan "Broadcast Yourself" was retired.

3rd logo 2013–present(Codename:The Dumb Ways To Die Logo)
In December 19, 2013, the red was made slightly lighter in color.

Website History
This is a look at YouTube over the years.

Yoodles
Like Google with their Doodles, YouTube changes their default logo to a stylized one with relevance to a certain date on various days throughout the year. These special logos are called Yoodles.