A summary of stock option and SAR activity for the six months ended June 30, 2025 is as follows (in millions, except share amounts which are reflected in thousands, per share amounts, and years):


	SARs Outstanding Number of SARs	Options Outstanding Number of Shares	Weighted-Average Exercise Price Per Share		Weighted-Average Remaining Contractual Life (in years)	Aggregate Intrinsic Value
As of December 31, 2024	33	7,198	$	40.16	4.90	$	153
Granted	—	484	$	74.44
Exercised	(9)	(1,029)	$	14.76
Canceled and forfeited	(3)	(141)	$	39.82
As of June 30, 2025	21	6,512	$	46.77	5.05	$	304
Exercisable as of June 30, 2025	21	2,694	$	26.98	3.37	$	180

The following table summarizes the activity related to our RSUs for the six months ended June 30, 2025 (in thousands, except per share amounts):


	Number of Shares	Weighted-Average Grant-Date Fair Value per Share
Unvested and outstanding as of December 31, 2024	66,202	$	48.49
Granted	30,509	$	74.84
Vested	(18,850)	$	44.95
Canceled and forfeited	(4,644)	$	52.55
Unvested and outstanding as of June 30, 2025	73,217	$	60.12

Stock-based compensation expense is allocated based on the cost center to which the award holder belongs. The following table summarizes total stock-based compensation expense by function (in millions):


	Three Months Ended June 30,				Six Months Ended June 30,
	2024		2025		2024		2025
Operations and support	$	54	$	59	$	121	$	111
Sales and marketing	24		28		45		52
Research and development	277		284		576		548
General and administrative	100		104		197		199
Total	$	455	$	475	$	939	$	910

As of June 30, 2025, there was $4.2 billion of unamortized compensation costs related to all unvested awards. The unamortized compensation costs are expected to be recognized over a weighted-average period of approximately 2.90 years.

The income tax benefits recognized in the condensed consolidated statements of operations for stock-based compensation expense were not material during the three and six months ended June 30, 2024 and 2025.

In February 2024, our board of directors authorized the repurchase of up to $7.0 billion in shares of our outstanding common stock (the “Share Repurchase Program”). The timing, manner, price and amount of any repurchases are determined by the discretion of management, depending on market conditions and other factors. Repurchases may be made through open market purchases and accelerated share repurchases. The exact number of shares to be repurchased by us, if any, is not guaranteed. Depending on market conditions and other factors, these repurchases may be commenced or suspended at any time or periodically without prior notice.

During the first quarter of 2025, we completed an accelerated share repurchase (“ASR”) to repurchase $1.5 billion of our outstanding common stock as part of our previously announced Share Repurchase Program.

During the three and six months ended June 30, 2025, we repurchased, and subsequently retired, 16.4 million and 42.9 million shares of common stock, respectively, for $1.4 billion and $3.2 billion, respectively, excluding broker commissions and fees. As of June 30, 2025, we had approximately $2.6 billion available to repurchase shares pursuant to the Share Repurchase Program.

The Inflation Reduction Act imposed a nondeductible 1% excise tax on the net value of certain stock repurchases. During the three and six months ended June 30, 2025, the excise tax on net share repurchases was not material.