The download is available to developers through Apple's official iOS developer portal. People familiar with the software say it is known as build 8F190.
Typically a gold master issued to developers is identical to the version that eventually becomes the final release, though two Golden Masters of iOS 4.2 were released after the first was found to have issues.
Improved iTunes Home Sharing will also allow users to access all of their content directly over Wi-Fi. And enhancements to AirPlay will allow applications and websites to stream over Wi-Fi to the Apple TV set top box. Sharing of photos over AirPlay can also use the built-in slide show options of iOS.
The new Personal Hotspot feature in iOS 4.3 lets users share their 3G data connection over Wi-Fi. Personal Hotspot will work with supporting carriers and monthly data plans on the iPhone 4.
iOS 4.3 also adds the ability to change the purpose of the hardware switch on the right side of the iPad and iPad 2. Users can choose to have the switch mute audio from the device, or have it serve as an orientation lock, as it originally did when the iPad first shipped last year.
The iOS 4.3 update is compatible with the iPhone 4, iPhone 3GS, first-generation iPad, iPad 2, and the third- and fourth-generation iPod touch. iTunes 10.2 has already been publicly released, adding compatibility with devices that are running iOS 4.3