Stock-based compensation expense was $286 million and $362 million for the three months ended September 30, 2023 and 2024, respectively, and $830 million and $1.0 billion for the nine months ended September 30, 2023 and 2024, respectively.

A summary of stock option and restricted stock unit (“RSU”) activity under the Company’s equity incentive plans was as follows (in millions, except per share amounts):


		Outstanding Stock Options			Outstanding RSUs
	Shares Available for Grant	Number of Shares	Weighted- Average Exercise Price		Number of Shares	Weighted- Average Grant Date Fair Value
As of December 31, 2023	134	7	$	71.76	30	$	85.35
Granted	(12)	1	168.18		11	156.31
Increase in shares available for grant	13	—	—		—	—
Options exercised/RSUs vested(1)	3	(2)	41.38		(7)	127.68
Canceled	2	—	—		(2)	143.43
As of September 30, 2024	140	6	$	88.11	32	$	96.73

In May 2023, 11.2 million stock options were exercised in cashless transactions pursuant to which the Company withheld and retired 5.7 million shares of common stock, valued at their fair market value on the exercise date, to cover the related $567 million of employee withholding taxes and $36 million of exercise cost.

The following table summarizes options outstanding and exercisable as of September 30, 2024 (in millions, except per share amounts and years):


	Number of Shares	Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Life (Years)	Aggregate Intrinsic Value
Options outstanding	6	$	88.11	5.48	$	296
Options exercisable	5	$	74.14	4.69	$	286