Safari 6.1 beta 5, or seed 5, for Mountain Lion was seeded to developers on August 7, 2013. 



This is pre-release beta software, and is subject to bugs and imperfections.



New features:

Safari Sidebar
The Safari Sidebar makes it easy to access your Bookmarks, Reading List, and 
Shared Links. (Shared Links on Mountain Lion only)

Shared Links (Mountain Lion only)
Shared Links shows you links from people you follow on Twitter. You can see 
who shared the link, as well as the comments they posted about it.

Continuous Reading (Mountain Lion only)
Continuously scroll through all the articles and webpages in your Reading List 
and in Shared Links. When you select an item and scroll to its last page, the 
next item in your list automatically appears below it.

Easy Retweet (Mountain Lion only)
A Retweet button in Shared Links makes it easy to retweet links from people 
you follow on Twitter.

Redesigned Top Sites
Top Sites has a new look and makes it easier than ever to get to your favorite 
websites. Rearrange sites by dragging and dropping thumbnails.

Safari Power Saver
Safari conserves energy by playing only the plug-in content that's front and 
center on the webpages you browse to. Safari displays a preview of the plug-in 
content on a webpage's margins, but waits until you click that content before 
running it, so you only use energy viewing the content you want to see.

Third-party data blocking
Safari blocks third-party websites from leaving data that could be used to track 
you online.

Faster Javascript
Thanks to the faster Nitro JavaScript engine in Safari, browsing is even faster 
and more responsive.

iCloud Tabs autocomplete (Mountain Lion only)
When you type into the Smart Search Field, Safari shows you webpages in your 
iCloud Tabs, making it even easier to pick up your browsing right where you 
left of on another device.

Yandex search built-in
Leading Russian search provider Yandex is a built-in option for Russian users, 
in addition to Google, Yahoo! and Bing.

Sandboxed plug-ins
Safari sandboxes popular plug-ins, making it safer to run them by restricting 
what they can do and what data they can access on your system. The Adobe 
Flash Player, Silverlight, QuickTime and Oracle Java plug-ins are sandboxed in 
Safari.

PDF sandboxing
Loading PDFs in Safari’s built-in PDF viewer is safer thanks to sandboxing. 
Sandboxing restricts what a file can do or access on your system, so if PDF file 
you view on the web contains malicious code, Safari can prevent it from 
harming your computer.