The Company has authorized the issuance of Class A common stock and Class B common stock. Holders of shares of Class A common stock are entitled to one vote per share, while holders of shares of Class B common stock are entitled to ten votes per share. Shares of the Company's Class B common stock are convertible into an equivalent number of shares of its Class A common stock and generally convert into shares of its Class A common stock upon transfer. The holders of Class A common stock and Class B common stock have no preemptive or other subscription rights and there are no redemption or sinking fund provisions with respect to such shares. Class A common stock and Class B common stock are referred to as "common stock" throughout these Notes to the Condensed Consolidated Financial Statements, unless otherwise noted. As of September 30, 2019, the Company was authorized to issue 1,000,000,000 shares of Class A common stock and 500,000,000 shares of Class B common stock, each with a par value of $0.0000001 per share. As of September 30, 2019, there were 346,552,092 shares of Class A common stock and 82,521,716 shares of Class B common stock outstanding. Options and awards granted following the Company's initial public offering are related to underlying Class A common stock.

In conjunction with the 2023 Notes offering, the Company sold the 2023 warrants whereby the 2018 Counterparties have the option to purchase a total of approximately 11.1 million shares of the Company’s Class A common stock at a price of $109.26 per share. The Company received $112.1 million in cash proceeds from the sale of the 2023 warrants. See Note 13, Indebtedness, for more details on this transaction.

In conjunction with the 2022 Notes offering, the Company sold warrants whereby the 2017 Counterparties have the option to purchase a total of approximately 19.2 million shares of the Company’s Class A common stock at a price of $31.18 per share. None of the warrants associated with the 2022 and 2023 Notes offering were exercised as of September 30, 2019.

The Company maintains two share-based employee compensation plans: the 2009 Stock Plan (2009 Plan) and the 2015 Equity Incentive Plan (2015 Plan). The 2015 Plan serves as the successor to the 2009 Plan. The 2015 Plan became effective as of November 17, 2015. Outstanding awards under the 2009 Plan continue to be subject to the terms and conditions of the 2009 Plan. Since November 17, 2015, no additional awards have been nor will be in the future granted under the 2009 Plan.

Under the 2015 Plan, shares of the Company's Class A common stock are reserved for the issuance of incentive and nonstatutory stock options, restricted stock awards (RSAs), restricted stock units (RSUs), performance shares, and stock bonuses to qualified employees, directors, and consultants. The awards must be granted at a price per share not less than the fair market value at the date of grant. Initially, 30,000,000 shares were reserved under the 2015 Plan, and any shares subject to options or other similar awards granted under the 2009 Plan that expire, are forfeited, are repurchased by the Company, or otherwise terminate unexercised, will become available under the 2015 Plan. The number of shares available for issuance under the 2015 Plan will be increased on the first day of each fiscal year, in an amount equal to the least of (i) 40,000,000 shares, (ii) 5% of the outstanding shares on the last day of the immediately preceding fiscal year, or (iii) such number of shares determined by the Company’s board of directors or a committee thereof. As of September 30, 2019, the total number of shares subject to stock options, RSAs and RSUs outstanding under the 2015 Plan was 21,822,262, and 82,968,841 shares were available for future issuance. As of September 30, 2019, the total number of shares subject to stock options, RSAs and RSUs outstanding under the 2009 Plan was 20,422,313.



	Number of Stock Options Outstanding		Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (in years)	Aggregate Intrinsic Value
Balance at December 31, 2018	33,152,881		$	9.52	5.45	$	1,543,793
Granted	1,184,657		72.15
Exercised	(7,881,289	)	7.97
Forfeited	(136,772	)	11.70
Balance at September 30, 2019	26,319,477		$	12.80	5.23	$	1,305,789

Options exercisable as of September 30, 2019	24,136,540		$	9.40	4.92	$	1,269,509

The fair value of stock options and employee stock purchase plan rights are estimated on the date of grant using the Black-Scholes-Merton option valuation model. The fair value of RSAs and RSUs is determined by the closing price of the Company’s common stock on each grant date.



	Three Months Ended September 30,				Nine Months Ended September 30,
	2019		2018		2019		2018
Cost of revenue	$	38	$	18	$	88	$	79
Product development	56,321		39,525		155,114		103,813
Sales and marketing	6,269		6,108		20,304		16,703
General and administrative	14,798		13,262		42,474		37,261
Total	$	77,426	$	58,913	$	217,980	$	157,856

The Company recorded $5.1 million and $14.1 million of share-based compensation expense related to the Company's 2015 Employee Stock Purchase Plan during the three and nine months ended September 30, 2019, respectively, compared to $2.0 million and $6.3 million for the three and nine months ended September 30, 2018, which are included in the table above.

The Company capitalized $2.4 million and $6.0 million of share-based compensation expense related to capitalized software costs during the three and nine months ended September 30, 2019, respectively, compared to $2.0 million and $6.3 million for the three and nine months ended September 30, 2018, respectively.