Maciej Stachowiak, of the WebKit development team, has announced that a version of the engine underlying Apple's Safari browser has become the first to fully pass the Acid3 test, including the smooth animation rendering test. Acid3 is a test page that scores how well a rendering engine follows defined web standards, including DOM and JavaScript. The test provides a metric for comparing different engines, and has pushed developers to work towards better performance.

In March the WebKit team announced that it had technically reached a 100/100 on Acid3, although this was not a perfect pass of the test. There was a slight glitch in the text rendering, and the animation was not as smooth as it could have been. The most recent release has fixed these bugs; Stachowiak gives credit to "recent speedups in JavaScript, DOM and rendering."

Though WebKit is used in browsers such as Safari and Chrome, it should be noted that neither program relies on the latest edition of the engine.