The Xperia U has a 3.5-inch (88.9 mm) touch-screen with the mobile BRAVIA engine which optimises the picture, a 1 GHz dual core processor, a 5 mega-pixel rear camera, 0.3 mega-pixel front camera, 512 MB of RAM, and 8 GB of internal storage.

It was revealed in late 2011 that Sony Ericsson was working on the ST25i,[1] and on 20 January 2012 a photo of a development model of the phone, codenamed Kumquat, was leaked.

The handset was introduced in Barcelona on 28 February 2012 before the Mobile World Congress in the United Kingdom in March 2012 and was released worldwide on 15 May 2012.

The device features a STE Nova Thor U8500 1 GHz dual core processor, 512 MB RAM(split into 392MB system memory and 120MB for the GPU), Mali-400 GPU, 8 GB of internal storage (4 GB of which is available to the user) and a micro-USB connector with USB-OTG support.

It is connected to the Sony Entertainment Network, allowing users to access Music & Video Unlimited in some parts of the world.

On 17 December 2012, Sony confirmed that the Xperia U will not be updated to Android Jelly Bean 4.1 due to hardware incompatibility.

[weasel words] Natasha Lomas of CNET gave the phone 4 out of 5, saying that "for Android lovers looking for a budget smartphone for dainty snacking on apps and mobile websites, the Xperia U is a worthy contender.

Some custom ROMs support file systems like NTFS for this storage, so large external hard drives can be used with the phone too.