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 funded from working capital. The Repurchase Program 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, 10b5-1 trading plans, 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 us at any time without prior notice. As of December 31, 2023, the remaining authorized amount for stock repurchases under this program was approximately $144.5 million.

The aggregate purchase price of repurchased shares of our common stock is recorded as a reduction to retained earnings in our 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 (the “2014 Plan Evergreen Increase”), unless the 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 for future issuance under the 2014 Plan. As of December 31, 2023, there remained approximately 95.3 million shares available for issuance under the 2014 Plan.

In April 2014, the 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 immediately preceding December 31, but not to exceed 10 million shares, unless the 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 for future issuance under the ESPP. As of December 31, 2023, there remained 23.4 million shares available for issuance under the ESPP. Furthermore, in February, 2024, our board of directors authorized an increase of 3.1 million shares for future issuance under the ESPP effective January 1, 2024.

Under our ESPP, eligible employees are permitted to acquire shares of our common stock at 85% of the lower of the fair market value of our common stock on the first trading day of each offering period or on the exercise date. Each offering period lasts approximately two years starting on the first trading date after February 15 and August 15 of each year, and includes purchase dates every six months on or after February 15 and August 15 of each year. Participants may purchase shares of common stock through payroll deductions up to 10% of their eligible compensation, subject to Internal Revenue Service mandated purchase limits.


	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	(3,310)	9.84
Options canceled	(2)	7.82
Balance—December 31, 2023	2,457	$	19.83	1.7	$	529,931
Vested and exercisable—December 31, 2023	2,247	$	18.14	1.5	$	488,319

We did not grant any stock options during the years ended December 31, 2023, 2022 and 2021. The aggregate intrinsic value of options exercised during the years ended December 31, 2023, 2022 and 2021 was $525.3 million, $311.7 million and $410.9 million, respectively. The total fair value of options vested for the years ended December 31, 2023, 2022 and 2021 was approximately $8.7 million, $16.6 million and $25.3 million, respectively.


	Number of Shares	Weighted- Average Grant Date Fair Value Per Share
Unvested balance—December 31, 2022	8,360	$	85.83
RSUs and PRSUs granted	2,664	157.94
RSUs and PRSUs vested	(2,862)	78.81
RSUs and PRSUs forfeited/canceled	(262)	100.46
Unvested balance—December 31, 2023	7,900	$	112.76

The weighted-average grant-date fair value of RSUs granted during the years ended December 31, 2023, 2022 and 2021 was $157.94, $101.35 and $93.18 per share, respectively. The total fair value of RSUs vested for the years ended December 31, 2023, 2022 and 2021 was approximately $225.5 million, $174.0 million, and $120.4 million, respectively.


	Year Ended December 31,
	2023		2022		2021
Cost of revenue	$	12,789	$	9,688	$	7,444
Research and development	172,177		130,897		99,770
Sales and marketing	71,074		57,571		46,521
General and administrative	40,716		32,778		33,140
Total stock-based compensation	$	296,756	$	230,934	$	186,875

We record stock-based compensation awards based on fair value as of the grant date. We value RSUs at the market close price of our common stock on the grant date. For option awards and ESPP offerings, we use the Black-Scholes option pricing model to determine fair value. We recognize such costs as compensation expense generally on a straight-line basis over the requisite service period of the award.