Google's parent company, Alphabet, has officially overtaken Apple as the world's most valuable company after it posted a market cap of around $570 billion, passing Apple's $535 billion.

"Our very strong revenue growth in Q4 reflects the vibrancy of our business, driven by mobile search as well as YouTube and programmatic advertising, all areas in which we've been investing for many years," Ruth Porat, Alphabet's CFO, told Tech Crunch.

Alphabet's value steadily gained in 2015 while Apple experienced a slowdown as its stock fell for the most part of the previous 12 months. Alphabet has also settled tax settlements, which led to the decline of the Alphabet's tax rate to just 17 percent, according to The Guardian.

The better performance of Google's core businesses also underpinned Alphabet's rise to the top. Gmail, for instance, recently breached its 1 billionth user mark, joining other Google services to achieve the feat such as YouTube, Android, Chrome and Google Play Store. The massive user base drives the uptick in the revenue generated from Alphabet's advertising business. Paid clicks has increased by 31 percent, a trend that is more likely to continue as most user activities shift to mobile devices, Tech Crunch reported.

This is not the first time Alphabet eclipsed Apple in terms of earning. From 2008 to 2010, Google and Apple outdid each other at some points before Apple pulled away in 2012 when its revenue soared due to the iPhone mania. At that point, the two companies were separated by more than $400 billion, according to CNBC.