In April 2013, then-Mozilla CEO Gary Kovacs said that Firefox would not come to iOS if Apple required the use of the WebKit layout engine to do so. One reason given by Mozilla was that prior to iOS 8, Apple had supplied third-party browsers with an inferior version of their JavaScript engine which hobbled their performance, making it impossible to match Safari's JavaScript performance on the iOS platform. Apple later opened their "Nitro" JavaScript engine to third-party browsers. In 2015, Mozilla announced it was moving forward with Firefox for iOS, with a preview release made available in New Zealand in September of that year. It fully released in November later that year. In November 2016, Firefox released a new iOS app titled Firefox Focus, a private web browser.