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macrumors bot
Original poster
Apr 12, 2001

Apple is apparently working on significant improvements to JavaScript performance for its Safari browser, as shown by the inclusion of accelerator upgrades in recent builds of WebKit, reports InfoWorld.

WebKit is the open source browser engine created by Apple and which serves as the basis for Safari, and the new upgrades to WebKit's "Nitro" JavaScript engine are known as "FTLJIT". With the upgrades, WebKit's JavaScript engine would become more competitive with Google's V8 and Mozilla's SpiderMonkey engines.
FTLJIT is still considered experimental, so although it's being made available in the OS X port of WebKit by default, it's not actually turned on yet -- it has to be enabled through command-line flags.

One attribute that could make FTLJIT stand out from the pack all the more is how well it runs JavaScript code that is not specifically optimized for [Mozilla's] asm.js. Every JavaScript engine will run asm.js code, but only Mozilla's SpiderMonkey honors asm.js-specific optimizations, and right now no other browser maker has elected to follow Mozilla's lead.
The report notes that speed tests are showing WebKit with FTLJIT enabled outperforming Chrome, while Firefox still tops the charts when using asm.js-optimized benchmark tests.

JavaScript has been a key technology for web browsers for many years, facilitating a variety of user interactions with web pages such as dynamic loading of content without reloading pages and handling page animations and other media. Because JavaScript code embedded on a website is run inside the user's browser when the page is loaded, the efficiency of the browser's JavaScript engine can have a significant impact on the user experience as JavaScript implementations become increasingly complex.

It is unclear whether Apple is targeting OS X 10.10 for these JavaScript improvements, but with them only being enabled in the OS X version of WebKit, it appears that there is still substantial work to be done.

Article Link: Apple Looking to Boost Safari JavaScript Performance with New Accelerator Upgrades


macrumors 68020
Sep 27, 2013
The reason I don't use Safari is due to the iCloud Keychain messages that keep popping up. If I press the "?" on the message box for the Keychain,it also crashes Safari. Anyone know how to stop this popup?


macrumors 604
Mar 11, 2013
Any improvement to Safari is welcome. It is my favorite browser and although it is notably faster with version 7 it still has this issue where it will randomly hang and I must quit and reopen it to regain performance.

BTW, that Safari icon matches the Gold iPhone 5S! :)


macrumors 601
Jun 22, 2006
The thick of it
This is good news. I had high hopes for HTML5. But when Google decided to fork HTML5, I was concerned that Safari might fall behind. Or at the least, we'd be end up with the old browser wars where web pages would looks completely different from browser to browser. I wish they'd just all play nice together. With Apple incorporating support for Mozilla's JS, maybe there's hope...


macrumors 6502a
May 10, 2005
I actually do think it's now enabled in the Webkit nightlies without any cli options. I just ran google Octane and the nightly was a whopping 49% faster than Safari 7.0.3 and even 3% faster than Chrome 34. This was not the case a month or so ago when I last tested.

This is going to make a much bigger difference when it lands in Mobile Safari.


macrumors G3
Feb 23, 2010
Is it still the case, on the iPad that Apple keep secret (thinks) that make it fast so that 3rd party web browsers can never compete?

Was there not something like that they did, or do ?


macrumors 68040
May 15, 2007
Does this apply to both OS X and iOS? If both, hopefully this could help with the iOS reloading issues some have experienced.
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