The Company’s 2016 Stock Option and Incentive Plan (the “2016 Plan”) provides for granting stock options, restricted stock units (“RSU”), restricted stock awards (“RSA”), stock appreciation rights, unrestricted stock awards, performance share awards, dividend equivalent rights and cash-based awards to its employees, directors and consultants. Certain of the Company’s outstanding equity awards were granted under equity incentive plans that are no longer active but continue to govern the outstanding equity awards granted thereunder.

The Company also offers an Employee Stock Purchase Plan (“ESPP”) to eligible employees. The ESPP provides for separate six-month offering periods beginning in May and November of each year. In the three months ended June 30, 2021 and 2020, 100,107 and 190,642 shares of Class A common stock were purchased under the ESPP, respectively, and 106,054 shares are expected to be purchased in the fourth quarter of 2021.

On January 1, 2021, the shares available for grant under the 2016 Plan and ESPP were automatically increased by 8,202,376 shares and 1,640,475 shares, respectively.

Stock-options and restricted stock units and awards activity under the Company’s equity incentive plans was as follows:


	Number of options outstanding	Weighted- average exercise price (Per share)		Weighted- average remaining contractual term (In years)	Aggregate intrinsic value (In thousands)
Outstanding options as of December 31, 2020	5,070,735	$	51.71	6.85	$	1,454,222
Granted	249,842	368.82

Exercised	(816,973)	39.06
Forfeited and canceled	(271,864)	117.93
Outstanding options as of June 30, 2021	4,231,740	$	68.62	6.43	$	1,377,618
Options vested and exercisable as of June 30, 2021	2,573,689	$	28.19	5.20	$	941,885


	Three Months Ended June 30,				Six Months Ended June 30,
	2021		2020		2021		2020
	(In thousands, except per share amounts)
Aggregate intrinsic value of stock options exercised (1)	$	100,425	$	338,031	$	265,984	$	406,390
Total estimated grant date fair value of options vested	$	45,873	$	17,684	$	77,852	$	41,020
Weighted-average grant date fair value per share of options granted	$	200.05	$	93.37	$	202.36	$	64.06

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(1) Aggregate intrinsic value represents the difference between the fair value of the Company’s Class A common stock as reported on the New York Stock Exchange and the exercise price of outstanding “in-the-money” options.

Additionally, as of June 30, 2021, the Company had outstanding 555,000 shares of performance-based stock options with a weighted average exercise price of $31.72, of which 555,000 were vested and exercisable. All performance conditions have been met.


	Number of awards outstanding	Weighted- average grant date fair value (Per share)		Aggregate intrinsic value (In thousands)
Unvested RSUs as of December 31, 2020	7,523,882	$	131.76	$	2,542,858
Granted	1,656,381	342.50

Vested	(1,754,042)	90.57
Forfeited and canceled	(418,114)	150.01
Unvested RSUs as of June 30, 2021	7,008,107	$	190.79	$	2,762,315

Additionally, as of June 30, 2021, the Company granted 24,697 shares of RSAs with a weighted average grant date fair value of $359.80 per share and aggregate intrinsic value of $9.7 million.

As of June 30, 2021, the Company had 258,554 shares of its Class A common stock in escrow that are subject to future vesting over a period of 2.3 years with a weighted average grant date fair value of $273.38 per share and aggregate intrinsic value of $101.9 million.


	Unrecognized Compensation Cost		Weighted-average remaining period
	(In thousands)		(In years)
Unvested stock options	$	203,631	2.4
Unvested restricted stock units and awards	1,217,788		3.1
Class A shares in escrow subject to future vesting	53,019		2.3
ESPP	7,150		0.4
Total	$	1,481,588

The fair value of employee stock options was estimated on the grant date using the following assumptions in the Black-Scholes option pricing model:


	Three Months Ended June 30,		Six Months Ended June 30,
Employee Stock Options:	2021	2020	2021	2020
Fair value of common stock	$316.3 - $367.7	$108.4 - $191.9	$316.30 - $409.20	$108.4 - $191.9
Expected term (in years)	6.08	6.08	6.08	6.08
Expected volatility	59.7%	54.7% - 56.0%	58.3% - 59.7%	51.9% - 56.0%
Risk-free interest rate	1.0% - 1.1%	0.4%	0.8% - 1.1%	0.4% - 1.4%
Dividend rate	—%	—%	—%	—%


	Three Months Ended June 30,		Six Months Ended June 30,
Employee Stock Purchase Plan:	2021	2020	2021	2020
Expected term (in years)	0.50	0.50	0.5	0.5
Expected volatility	58.7%	72.1%	58.7%	72.1%
Risk-free interest rate	0.04%	0.2%	0.04%	0.2%
Dividend rate	—%	—%	—%	—%


	Three Months Ended June 30,				Six Months Ended June 30,
	2021		2020		2021		2020
	(In thousands)
Cost of revenue	$	3,024	$	2,143	$	5,741	$	3,980
Research and development	58,871		39,841		115,830		73,050
Sales and marketing	47,940		23,086		89,576		43,029
General and administrative	34,333		14,317		70,176		28,353
Total	$	144,168	$	79,387	$	281,323	$	148,412