The company has been the web's biggest draw for advertisers for a decade, enabling it last month to become the fourth listed company to top $1 trillion in market capitalization.

But new concerns have emerged among investors about whether Google's dominance will last as United States antitrust regulators investigate Google and as Amazon.com Inc and Facebook Inc continue to grow their ads businesses globally.

Over the last year, Google has posted slowing sales growth for its ad business. It has blamed foreign exchange rates and one-time product changes.

Expenses have ballooned with the hiring of thousands of salespeople, the building of new data centres, and the marketing of the Google brand through hardware and other ventures.

The fourth-quarter results continued those trends.

Overall sales were $46.08bn, up 17 percent, compared with an average estimate of $46.94bn among financial analysts tracked by Refinitiv.

Google ad sales were $37.93bn, up 16.7 percent from the same period last year, while Google's "other" revenue bucket, including app store purchases and cloud computing deals, rose 21.6 percent to $7.88bn.

Alphabet's total costs and expenses rose 18.5 percent from a year ago to $36.809bn.

That left profit of $10.67bn, or $15.35 per share, compared with the analysts' average estimate of $8.787bn, or $12.53 per share.

Google faces internal challenges, too. Some of its 119,000 employees have resisted working on weapons-related software for militaries or censored search products for Chinese users, leading Google to abandon such efforts. Others have expressed frustration with curbs on company-wide discussions and what they have described as retaliation for labour organising.

In December, Google Chief Executive Sundar Pichai gained the additional role of Alphabet CEO from Larry Page as he and fellow cofounder Sergey Brin stepped back even further from day-to-day management.

It is unclear whether Pichai plans major changes to quell workplace unrest. But a shareholder lawsuit, which alleges that company leaders covered up sexual misconduct at Google, recently entered mediation and threatens to loosen the control held by Pichai, Page and Brin.

On Monday, Pichai's new role brought with it changes to Alphabet's financial disclosures, which investors before generally criticised as being too opaque to explain how the company is weathering specific challenges.

Shares of Alphabet were up 28.1 percent in the last 12 months entering Monday, compared with 21.8 percent for Facebook shares, 23.5 percent for Amazon, 68.1 percent for Microsoft Corp, and 88.7 percent for Apple Inc.