Google has leapfrogged over Apple to take the top spot in a global ranking measuring the value of the world's biggest brands. Google saw a 40 percent year-on-year increase and is now worth to $159 billion, putting it atop Brown Optimor's annual BrandZ list of the 100 most-valuable global brands, commissioned by WPP. The study calculates brand value by looking at its potential and current buyers alongside financial data. Read MoreGoogle tries to buy its way into the enterprise



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"Google has been hugely innovative in the last year with Google Glass, investments in artificial intelligence and a multitude of partnerships that see its Android operating system becoming embedded in other goods such as cars," Millward Brown Optimor managing director Nick Cooper said in a statement. Apple was knocked from the top after a three-year reign, after its brand's value fell 20 percent to $148 billion. The report said a perception that the Silicon Valley giant no longer redefines technology for its customers, as evidenced by a lack of new product launches, was behind the dip. Still, the fact Google and Apple took first and second place reflects technology brands' growing dominance. Read MoreThe charts say to avoid Apple, embrace IBM

Tech accounted for the top 4 spots, with IBM and Microsoft ranked third and fourth, respectively. And all together, technology brands were worth the most for the year, at $841.5 billion compared with telecoms at $330 billion and retail with $280 billion. They trumped regional banks ($251 billion), global banks ($124 billion) and personal banks ($111.5 billion), whose brands recovered after the fallout from the global financial crisis.