Alphabet Inc has reported better-than-expected quarterly profit, sending shares of Google's parent soaring in after-hours trading and making it the most valuable US company ahead of rival Apple Inc.
It was the first quarter the company provided information on what it calls "Other Bets" such as self-driving cars, and the solid results eased investor concerns about the company's spending on ambitious projects.
"As long as the core business continues to operate well with accelerated revenue... investment in those businesses can continue," said Ronald Josey of JMP Securities.
Alphabet said consolidated revenue jumped 17.8 per cent to $US21.33 billion ($A30.04 billion) in the fourth quarter ended December 31, from $US18.10 billion a year earlier. Analysts had expected $US20.77 billion.
Total operating losses on the Other Bets - which include glucose-monitoring contact lenses and Internet balloons - increased to $US3.57 billion in the 12 months ended December 31, and $US1.2 billion in the fourth quarter.
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In a call with analysts, Chief Financial Officer Ruth Porat attributed the strong earnings to "increased use of mobile search by consumers", as well as "ongoing momentum" in YouTube and programmatic advertising.
Google's shares were up almost 6 per cent at $US795.68 in after-hours trading, after breaking through the $US800 level.
Alphabet's combined share classes were worth $US555 billion, compared with Apple, which had a value of about $US534 billion.
Alphabet will officially overtake Apple in market value if both companies' shares open around current levels on Tuesday.
Google's advertising revenue increased nearly 17 per cent to $19.08 billion, while the number of ads, or paid clicks, rose 31 per cent, the company said. Analysts had expected paid clicks to increase 21.8 per cent.
Advertisers pay Google only if someone clicks on their ad.
Net income in the fourth quarter rose to $US4.92 billion, or $US7.06 per Class A and B share and Class C capital stock, from $US4.68 billion, or $US6.79 per share.
Adjusted earnings of $US8.67 per share excluded certain one-time items.
