Apple today seeded build 12F20 of OS X 10.8.5 to developers, offering a fourth version of the next Mac operating system update for testing. The release comes one week after the appearance of the previous beta of OS X 10.8.5, build 12F17.

Mountainlion12f20
As with previous betas, the update comes with no known issues and can be downloaded via Apple's Developer Page or through the software update tool in the Mac App Store.

Testing on OS X 10.8.5 comes as Apple is also continuing work on its next major version of OS X, Mavericks. Apple has already seeded three developer previews of OS X Mavericks and has announced that it will launch the new operating system to the public this fall.

Update: One tipster says the update fixed the Adobe Photoshop flickering issue that was reported last last month.

Top Rated Comments

gnurf Avatar
161 months ago
A pretty irrelevant post considering this a about Mavericks, not iOS.

Except it isn't about Mavericks :)
Score: 7 Votes (Like | Disagree)
HolgerR Avatar
161 months ago
A pretty irrelevant post considering this a about Mavericks, not iOS.

No. It's not.
Score: 3 Votes (Like | Disagree)
ValSalva Avatar
161 months ago
Will there be a 10.8.6?

Yays? Nays?

I think yes. 10.8.5 will be out well before Mavericks. Then work on 10.8.6 will begin. I highly doubt there will be any 10.8.7 though.
Score: 2 Votes (Like | Disagree)
cbs20 Avatar
161 months ago
Have any of you guys any experience in how things are running with the latest 10.8.5 vs the 10.9 dev ?

I had the first 10.9 dev build installed and it runs like a dream, but things like some adobe apps breaks, but I would hate going back to 10.8 (standard) because that was dreadful too... so currently i am running windows8.1 but would prefer to get back on a speedy osx :)

So if any of you for some reason have had too much time and have a feeling of both, let me know! thanks :P

First thing you have to consider is 10.8 is a much more established OS and 10.9 is only in beta. When DP1 for 10.9 was released that was the first time anybody at Adobe could get their hands on the OS and start optimizing applications to run in 10.9. On top of that the OS is constantly changing until its final release and applications may need to be tweaked with these changes to make sure they work with the OS. You can't make a good comparison of a beta OS to an established OS. Wait until 10.9 is released and app developers release their updates and then you can judge what OS to use.
Score: 1 Votes (Like | Disagree)
Mr. Wonderful Avatar
161 months ago
^As much as I hate waiting longer for new releases, I think year and a half OS X development cycles might be a good thing for everyone. It's more time to add more significant features, and it allows more time for the current OS to become rock solid, which is great for casual users and enterprise. I know I felt like Lion never got truly stable.
Score: 1 Votes (Like | Disagree)
Garrod Avatar
161 months ago
They should do weekly iOS 7 beta seeds too.

A pretty irrelevant post considering this a about Mavericks, not iOS.
Score: 1 Votes (Like | Disagree)

Popular Stories

2024 iPhone Boxes Feature

Apple Adjusts Trade-In Values for iPhones, iPads, Macs, and More

Thursday November 6, 2025 11:12 am PST by
Apple today updated its trade-in values for select iPhone, iPad, Mac, and Apple Watch models. Trade-ins can be completed on Apple's website, or at an Apple Store. The charts below provide an overview of Apple's current and previous trade-in values in the U.S., according to its website. Maximum values for most devices either decreased or saw no change, but the iPad Air received a slight bump. ...
Finder Siri Feature

Apple's New Siri Will Be Powered By Google Gemini

Wednesday November 5, 2025 11:57 am PST by
The smarter, more capable version of Siri that Apple is developing will be powered by Google Gemini, reports Bloomberg. Apple will pay Google approximately $1 billion per year for a 1.2 trillion parameter artificial intelligence model that was developed by Google. For context, parameters are a measure of how a model understands and responds to queries. More parameters generally means more...
iOS 26

iOS 26.1 Available Now With These 8 New Features

Monday November 3, 2025 5:54 am PST by
Following more than a month of beta testing, Apple released iOS 26.1 on Monday, November 3. The update includes a handful of new features and changes, including the ability to adjust the look of Liquid Glass and more. Below, we outline iOS 26.1's key new features. Liquid Glass Toggle iOS 26.1 lets you choose your preferred look for Liquid Glass. In the Settings app, under Display...
Liquid Glass General Feature

Apple Shares Liquid Glass Design Gallery

Thursday November 6, 2025 2:45 pm PST by
Apple is promoting the new Liquid Glass design in iOS 26, showing off the ways that third-party developers are embracing the aesthetic in their apps. On its developer website, Apple is featuring a visual gallery that demonstrates how "teams of all sizes" are creating Liquid Glass experiences. The gallery features examples of Liquid Glass in apps for iPhone, iPad, Apple Watch, and Mac. Apple...
airtag purple

Apple's Website Lists AirTag 4-Pack at Shockingly Low Price [Updated]

Friday November 7, 2025 6:40 am PST by
Apple's online store in the U.S. is suddenly offering a pack of four AirTags for just $29, which is the same price as a single AirTag. This is likely a pricing error, and it is unclear if orders will be fulfilled. Apple has not discounted the AirTag four-pack in any other countries that we checked. Delivery estimates are already pushing into late November to early December, suggesting...
apple watch se 3 always on

Apple to Remove iPhone-Apple Watch Wi-Fi Sync in EU With iOS 26.2

Thursday November 6, 2025 4:37 am PST by
Apple in iOS 26.2 will disable automatic Wi-Fi network syncing between iPhone and Apple Watch in the European Union to comply with the bloc's regulations, suggests a new report. Normally, when an iPhone connects to a new Wi-Fi network, it automatically shares the network credentials with the paired Apple Watch. This allows the watch to connect to the same network independently – for...
ikea smart home devices

IKEA Debuts 21 HomeKit-Compatible Smart Bulbs, Sensors, and Controls

Thursday November 6, 2025 4:08 pm PST by
IKEA today announced the upcoming launch of 21 new Matter-compatible smart home products that will be able to interface with HomeKit and the Apple Home app. There are sensors, lights, and control options, all of which will be reasonably priced. Some of the products are new, while some are updates to existing lines that IKEA previously offered. There are a series of new smart bulbs that are...
Home Hub Command Center with Dome Base Feature

Apple's 2026 Smart Home Revamp: All the Rumors

Wednesday November 5, 2025 3:54 pm PST by
It's been over a decade since Apple's HomeKit smart home platform launched, and it is overdue for an update. HomeKit and the Home app can no longer keep up with AI-powered solutions from other companies like Google and Amazon, but that's set to change with a smart home revamp that Apple has planned for 2026. Home Hub Apple is working on a home hub or "command center" that will serve as a...