samsung beginning coming from the month of march ought to unleash android 4. 2. 1 jelly bean for galaxy s 3 and these days just like the sign as to the official firmware is released, galaxy s3 get the very initial few leaked firmware based mostly by the latest major unleash of android. the firmware is accessible for your own flash via odin thanks to your user forum of xda-developers.

I9300XXUFMB3firmware for galaxy s 3 is predicated on android 4. 2. 1 jelly bean and is the internal system dump provided by xda user, that deserves a large amount of thanks.
still don't apprehend the most innovations of one's firmware however according to firmly initial reports the changelog could be composed of :

• 4.2.1 Android – build JOP40D
• Improved ripple effect in lockscreen
• Lockscreen with support for widgets
• Daydream
• What's new in the notification Center
• New voice commands for galaxy s3 to use

Here is the link from where you can download the file to flash.
I9300XXUFMB3 if you don't know how to flash it read how to flash cwm to galaxy s3. SamMobile wants to point out that the firmware is not yet a final version actually has some minor bug fixes but it is perfectly usable for daily use. Take also the binary counter in "modified" and being a no brand version will not install any modems, which will remain the one already used.
To install I recommend to follow this short guide (do with your own risk)

Install Android 4.2.1 To Galaxy S3

• Open Odin 3.04;
• Restart the phone in download mode (Home, Power and Vol Down);
• Connect your smartphone to your computer and wait until the connection recognized by Odin;
• Add the PDA archive (check both put the checkmark to repartition);
• Start the flash;

Here are some screenshot
 If you want to know when the release of official android 4.2.1 for Samsung Galaxy S3, you can subcrive to this blog, or follow us. We will update when the official 4.2.1 is released