Windows Live Search
The first public beta of Windows Live Search was unveiled on March 8, 2006, with the final release on September 11, 2006, replacing MSN Search.
On March 21, 2007, Microsoft announced that it would separate its search developments from the Windows Live services family, rebranding the service as Live Search.
In 2008, Microsoft recognised that there would be a brand issue as long as the word "Live" remained in the name. As an effort to create a new identity for Microsoft's search services, Live Search was officially replaced by Bing on June 3, 2009. Brand New ranked this the worst logo of 2009.
Just a few months before the new logo came out, another logo was unveiled on April 29, 2013, at the Design Day 2013 event. The logo resembles that of a flying boomerang, next to the name. Supposed to be used in 2013, but it wasn't used. The logo can be seen here, at 30:18.
Bing revealed a new logo on September 17, 2013, it was rolled out in the following weeks. It was still used on the website for a short time after the 2016 logo was introduced.
A new Bing logo was launched on January 14th, 2016. Used in tandem with the previous logo until February 2016. It looks similar to the previous logo but with different colours, the lowercase B was capitalized (like the 2013 logo that went unused) and the 'b' in the symbol was modified slightly.
This logo is similar to the 2013 logo, but with the colours of the 2016 logo. This logo was short-lived.
Now the logo is very similar to the main logo, but with a lighter end.
Still used on some portals.