In October 2021, our board of directors authorized a $1.0 billion stock repurchase program (the “Repurchase Program”). This authorization allows us to repurchase shares of our common stock that will be funded from working capital and expires in the fourth quarter of 2024. Repurchases may be made at management’s discretion from time to time on the open market, through privately negotiated transactions, transactions structured through investment banking institutions, block purchases, trading plans under Rule 10b5-1 of the Securities Exchange Act of 1934, as amended (the "Exchange Act"), or a combination of the foregoing. The Repurchase Program does not obligate us to acquire any of our common stock and may be suspended or discontinued by the company at any time without prior notice. As of September 30, 2023, the remaining authorized amount for stock repurchases under the Repurchase Program was approximately $144.5 million.

We did not repurchase any shares during the three months ended September 30, 2023. A summary of the stock repurchase activity under the Repurchase Program for the nine months ended September 30, 2023 is as follows (in thousands, except per share amounts):

The aggregate purchase price of repurchased shares of our common stock is recorded as a reduction to retained earnings in our unaudited condensed consolidated statements of stockholders' equity. All shares repurchased have been retired.

In April 2014, our board of directors and stockholders approved the 2014 Equity Incentive Plan (the “2014 Plan”), effective on the first day that our common stock was publicly traded, and simultaneously terminated the 2004 and 2011 equity plans as to future grants; however, these plans will continue to govern the terms and conditions of the outstanding options previously granted thereunder.

Awards granted under the 2014 Plan could be in the form of Incentive Stock Options (“ISOs”), Nonstatutory Stock Options (“NSOs”), Restricted Stock Units (“RSUs”), Restricted Stock Awards (“RSAs”) or Stock Appreciation Rights (“SARs”). The number of shares available for grant and issuance under the 2014 Plan increases automatically on January 1 of each year commencing with 2016 by the number of shares equal to 3% of the outstanding shares of our common stock on the immediately preceding December 31, but not to exceed 50 million shares, unless our board of directors, in its discretion, determines to make a smaller increase. Effective January 1, 2023, our board of directors authorized an increase of 9.2 million shares to the shares available for issuance under the 2014 Plan. As of September 30, 2023, there remained approximately 96.5 million shares available for issuance under the 2014 Plan.

In April 2014, our board of directors and stockholders approved the 2014 Employee Stock Purchase Plan (the “ESPP”). The ESPP became effective on the first day that our common stock was publicly traded. The number of shares reserved for issuance under the ESPP increases automatically on January 1 of each year by the number of shares equal to 1% of our shares outstanding on the immediately preceding December 31, but not to exceed 10 million shares, unless our board of directors, in its discretion, determines to make a smaller increase. Effective January 1, 2023, our board of directors authorized an increase of 3.1 million shares to the shares available for issuance under the ESPP. During the nine months ended September 30, 2023, we issued 279,498 shares at a weighted-average purchase price of $105.69 per share under the ESPP. As of September 30, 2023, there remained approximately 23.4 million shares available for issuance under the ESPP.


	Number of Shares Underlying Outstanding Options	Weighted- Average Exercise Price per Share		Weighted- Average Remaining Contractual Term (in years)	Aggregate Intrinsic Value
Balance—December 31, 2022	5,769	$	14.09	2.0	$	618,774
Options granted	—	—
Options exercised	(2,694)	9.00
Options canceled	(2)	8.10
Balance—September 30, 2023	3,073	$	18.56	1.8	$	508,139
Vested and exercisable—September 30, 2023	2,799	$	16.61	1.5	$	468,286


	Number of Shares	Weighted- Average Grant Date Fair Value Per Share		Weighted-Average Remaining Contractual Term (in years)	Aggregate Intrinsic Value
Unvested balance—December 31, 2022	8,360	$	85.83	1.7	$	1,014,431
RSUs granted	2,575	156.34
RSUs vested	(2,166)	78.49
RSUs forfeited/canceled	(235)	98.72
Unvested balance—September 30, 2023	8,534	$	109.13	1.9	$	1,569,587


	Three Months Ended September 30,				Nine Months Ended September 30,
	2023		2022		2023		2022
Cost of revenue	$	3,717	$	2,992	$	9,516	$	6,613
Research and development	47,965		37,698		125,671		93,723
Sales and marketing	20,490		16,103		51,461		42,039
General and administrative	13,218		8,684		28,750		23,605
Total stock-based compensation	$	85,390	$	65,477	$	215,398	$	165,980