YouTube

2005–2012
YouTube's first and currently longest-used logo consisted of the site's name in the Alternate Gothic typeface, with the word "Tube" being placed inside a red rounded rectangle, representing a television. This logo is still being used on some pages.

2012–2014
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. It has the red square in a darker color this time. Also, starting in late November 2012, the slogan "Broadcast Yourself" was retired.

2014–2015
On December 19, 2013, the red rectangle was made lighter in color. Also, the word "You" was made more black and the shadow behind the word "Tube" was removed. This is still used as a secondary logo.

2015–2017
YouTube's logo became purely two-dimensional in October 2015, with the introduction of its paid subscription service YouTube Red. This redesign may have also been made to be in line with Google's "Material Design" design language.

2017–present
On August 29, 2017, YouTube launched its most significant logo update yet, consisting of the wordmark in "almost black" (#282828) and a slightly modified typeface placed to the right of YouTube's priorly redesigned universal icon, the play button, whose color is now pure red (#FF0000). The logo change accompanies a set of new experiments YouTube is set to roll out over the next few months. On August 31, 2017 comment section was updated.

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