The UC Browser or UCWeb is a Chinese mobile browser first released in 2004. Initially it used a server proxy compression to speed up page rendering, using its own proprietary rendering engine (U1 + U2) and minimize data load. It currently has a leading market share in China and India.

While proxy is still an option on some devices, the browser apears to be using the native rendering engine (WebKit/Blink) on both iOS and Android devices . On Windows Phone it uses the Trident engine. The UC mini for Android apears to be based on the Opera Mini rendering engine. The UC Browser has also been released for Windows desktop computers using WebKit. In all cases the browser indicated the rendering engine but it should be clear that coding for UC is a bit of a mess.

There are plenty of rumors that the server compression has had some leaks and it is sending data un-encrypted along with unique identification. It has the look of a "perfect" surveillance tool and personally I would avoid using it.
https://citizenlab.org/2015/05/a-chatty-squirrel-privacy-and-security-issues-with-uc-browser/

The Mobile Browser

Version 1 to 7

This is a very simple mobile browser with limited JavaScript and CSS support, though the later versions do see a lot of improvements everything is still parsed (and obscured) through the proxy. Keep it simple.

These versions were released from 2004 to 2011.

Categorized as: mobile_light

Version 8 to 10

Released for most feature phone platforms, these versions has a an improved rendering engine (U2) but still uses the proxy system, thus debugging is extremely difficult and documentation is virtually non-existant.

These versions were released from 2011 to 2015.

Categorized as: mobile

Version 8 to 10 on iOS + Android

Using the native rendering engine and thus identified as either the Safari or the Chrome/Android browser.

These versions were released from 2011 to 2015.

Categorized as: Safari / Chrome on smartphone

The Desktop Browser

Version 5

Only released for Windows using the Webkit rendering engine. UC says it should be at version 5 currently, but I am also seeing a version 9 on Desktop in my stats (also using WebKit). Maybe 5 and 9 looks alike in Chinese.

This version was released in 2015.

Categorized as: Chrome / IE