I cannot tell from the Opera Desktop team blog or from the Presto Wikipedia page if Opera 12.15 is utilizing the WebKit or Presto rendering engine. The phrasing from Wikipedia can be interpreted either way:It [Presto] remained in use until Opera 12.15, when the browser's developer  Opera Software ASA began phasing Presto out of its products in favor  of the WebKit layout engine and V8 JavaScript engine combined with a  modified Chromium browser.Is Opera Version 12.15 using WebKit or Presto?
Is Opera Version 12.15 using WebKit or Presto for its rendering engine?
browsers
12.15 is still using Presto, but it's being phased out after 12.15 in favour of WebKit Blink, a WebKit fork.