Pursuant to our restated certificate of incorporation, as of June 30, 2021, the Board had the authority to issue up to a total of 100,500,000 shares of common stock. Each holder of common stock is entitled to one vote per share on any matter that is submitted to a vote of stockholders. In addition, holders of our common stock will vote as a single class of stock on any matter that is submitted to a vote of stockholders.

In May 2018, the Board authorized us to repurchase up to $300.0 million of our common stock under our share repurchase program. During the three and six months ended June 30, 2021 and 2020, we did not purchase any shares under the program. As of June 30, 2021, up to $245.0 million of common stock remained available for purchase under our program. The timing and amount of share repurchases, if any, will be determined based on market conditions, limitations under the Amended Credit Agreement, share price, available cash and other factors, and the share repurchase program may be terminated at any time.

The Groupon, Inc. Stock Plans (the "Plans") are administered by the Compensation Committee of the Board (the "Compensation Committee"). As of June 30, 2021, 2,763,276 shares of common stock were available for future issuance under the Plans.

The stock-based compensation expense related to stock awards issued under the Plans are presented within the following line items of the condensed consolidated statements of operations for the three and six months ended June 30, 2021 and 2020 (in thousands):


	Three Months Ended June 30,				Six Months Ended June 30,
	2021		2020		2021		2020
Cost of revenue	$	190	$	81	$	361	$	340
Marketing	178		(33)		313		841
Selling, general and administrative	9,370		8,495		16,243		21,377
Restructuring and related charges	—		1,424		—		1,424
Total stock-based compensation expense	$	9,738	$	9,967	$	16,917	$	23,982

We capitalized $1.1 million and $1.2 million of stock-based compensation for the three months ended June 30, 2021 and 2020, and $2.0 million and $2.3 million for the six months ended June 30, 2021 and 2020 in connection with internally-developed software and cloud computing arrangements.

The Groupon, Inc. 2012 Employee Stock Purchase Plan, as amended, ("ESPP") authorizes us to grant up to 1,000,000 shares of common stock under that plan as of June 30, 2021. For the six months ended June 30, 2021 and 2020, 23,418 and 28,621 shares of common stock were issued under the ESPP.

The restricted stock units granted under the Plans generally have vesting periods between one and four years and are amortized on a straight-line basis over their requisite service period.


	Restricted Stock Units	Weighted-Average Grant Date Fair Value (per unit)
Unvested at December 31, 2020	1,853,007	$	31.91
Granted	901,603	43.07
Vested	(929,616)	28.47
Forfeited	(193,507)	36.09
Unvested at June 30, 2021	1,631,487	$	39.38

As of June 30, 2021, $52.8 million of unrecognized compensation costs related to unvested restricted stock units are expected to be recognized over a remaining weighted-average period of 1.16 years.

We grant performance share units under the Plans that vest in shares of our common stock upon the achievement of financial and operational targets specified in the respective award agreement ("Performance Share Units"). During the year ended December 31, 2019, we also granted performance share units subject to a market condition ("Market-based Performance Share Units").

Our Performance Share Units and Market-based Performance Share Units are subject to continued employment through the performance period dictated by the award and certification by the Compensation Committee that the specified performance conditions have been achieved.


	Performance Share Units	Weighted-Average Grant Date Fair Value (per unit)		Market-based Performance Share Units	Weighted-Average Grant Date Fair Value (per unit)
Unvested at December 31, 2020	124,709	$	29.73	57,668	$	60.60
Granted (1)	41,729	15.44		—	—
Vested	(86,710)	24.36		—	—
Forfeited	(282)	69.00		—	—
Unvested at June 30, 2021	79,446	27.95		57,668	60.60

Maximum shares issuable upon vesting at June 30, 2021	79,446			57,668

(1)Performance Share Units granted during the six months ended June 30, 2021 relate to the issuance of incremental shares upon the Compensation Committee's certification of the achievement of the 2020 performance metrics.

As of June 30, 2021, $0.8 million of unrecognized compensation costs related to unvested Performance Share Units are expected to be recognized over a remaining weighted-average period of 1.17 years. We have recognized all compensation costs related to our unvested Market-Based Performance Share Units.