I have a very simple setup on my Macbook Pro. Ever since recent Safari updates it has been really underperforming.
As soon as I start safari with no web page "about:blank" is my default page or anything the CPU pegs at 200+% and comes down to 133% and just stays
there. The CPU fan is running constant if I leave Safari on. As soon as I close Safari all performance is back to normal.
OS X Yosemite (10.10.2)
Howdy erica
I have always hated something that reports anything greater than 100% !! 100% is ALL of anything!!
I am guessing you are getting your resource usage from Activity Monitor.app (?)
In Safari/Preferences/Search under "Smart Search Field:" turn OFF "Show Favorites".
Fixed it here (10.10.5, Safari 9.0.1)
There were two issues that I found.
1. Kerberos authentication made some of the favorites sites freeze that it was trying to display as an icon or thumbnail.
2. Safari was waiting with multiple dead connections to our Proxy server.
Seems like quite a silly bug that Safari developers should watch out and fix!
Use a different browser - I favor Firefox (Mozilla is oldie but a goodie)
Safari 9.0 at 100+% CPU , no plugins no addons and no flash
