The following table presents the detail of stock-based compensation expense amounts included in our consolidated statements of operations for the periods presented (in thousands):


	Year Ended December 31,
	2025		2024		2023
Cost of revenue	$	2,042	$	2,034	$	1,869
Research and development expense		27,012		25,666		21,307
Sales and marketing expense		6,653		10,774		10,240
General and administrative expense		19,556		18,072		14,570
Total stock-based compensation expense	$	55,263	$	56,546	$	47,986

In June 2016, our board of directors adopted and our stockholders approved our 2016 Equity Incentive Plan, or the 2016 Plan, which became effective in July 2016 at which time the 2010 Equity Incentive Plan, or the 2010 Plan, was terminated. The number of shares of common stock reserved for issuance under the 2016 Plan may increase on January 1 of each year, beginning on January 1, 2017 and ending on and including January 1, 2026, by the lesser of (1) 1,825,000 shares; (2) 5% of the total number of shares of common stock outstanding on December 31 of the preceding calendar year; and (3) a lesser number of shares determined by our board of directors. The 2016 Plan provides for granting incentive or non-qualified stock options, restricted stock, restricted stock units, stock appreciation rights and performance shares or performance units to employees, non-employee directors and consultants. We have not issued options or PSUs under the 2016 Plan since the year ended December 31, 2021 and December 31, 2023, respectively.

All options historically granted under the 2010 Plan and the 2016 Plan have a maximum 10-year term and generally vest and become exercisable over four years of continued employment or service as defined in each option agreement. As allowed under the 2016 Plan, there are a few exceptions to this vesting schedule, which permit vesting at different rates or based on achieving performance targets. We use newly issued shares to satisfy option exercises. As of December 31, 2025, we had approximately 4.7 million shares of common stock available for future grants.

The following table summarizes option award activity for the year ended December 31, 2025 (in thousands, except per share data and years):


	Number of Underlying Shares			Weighted-Average Exercise Price Per Share		Weighted-Average Remaining Contractual Life (Years)		Total Intrinsic Value
Outstanding at December 31, 2024		787		$	26.28		4.24	$	93,654
Granted		—			—
Exercised		(349	)		24.54
Forfeited or expired		—			—
Outstanding at December 31, 2025		438			27.67		3.65		64,054
Vested and exercisable at December 31, 2025		438		$	27.67		3.65	$	64,054

The total intrinsic value of options exercised during 2025, 2024 and 2023 was $38.9 million, $85.1 million and $19.1 million, respectively. The total grant date fair value of options vested was immaterial during 2025 and $1.0 million and $3.3 million during 2024 and 2023, respectively.

As of December 31, 2025, there was no unrecognized stock-based compensation cost related to unvested stock options.

The following table summarizes activity for restricted stock units, or RSUs and MSUs for the year ended December 31, 2025 (in thousands, except per share data):


	Number of Underlying Shares						Weighted-Average Grant Date Fair Value
	RSUs			MSUs			RSUs		MSUs
Outstanding at December 31, 2024		920			239		$	111.50	$	192.06
Granted		397			105			109.69		156.70
Vested		(459	)		(87	)		101.19		106.89
Forfeited		(87	)		(38	)		106.76		200.53
Outstanding at December 31, 2025		771			219		$	117.24	$	220.35

We record stock-based compensation expense for RSUs and MSUs on a straight-line basis over the requisite service period, which is generally the vesting period. Forfeitures are recognized as they occur.

In fiscal year 2022, we transitioned to a bonus plan that was half cash and half PSUs. The number of annual PSUs that ultimately vest depends on us attaining certain financial metrics for the fiscal year as well as on the employee’s continued employment through the vesting date. In fiscal year 2023, we transitioned to an all cash bonus plan.

The following table summarizes information related to granted and vested RSUs, PSUs and MSUs (in thousands, except per share data):


	Year Ended December 31,
	2025		2024		2023
RSU weighted-average grant date fair value	$	109.69	$	134.76	$	119.12
MSU weighted-average grant date fair value		156.70		160.32		145.51
PSU weighted-average grant date fair value	$	—	$	—	$	—

Fair market value of RSUs vested	$	57,836	$	74,358	$	64,417
Fair market value of MSUs vested		8,813		9,829		7,219
Fair market value of PSUs vested	$	—	$	—	$	7,261

As of December 31, 2025, our total unrecognized stock-based compensation cost related to unvested MSUs was $23.5 million, which we will recognize over the weighted-average period of 1.3 years. As of December 31, 2025, there was $81.2 million of total unrecognized compensation cost related to unvested RSUs, which we expect to recognize over a weighted-average period of 2.5 years.

Effective July 2016, we adopted the 2016 Employee Stock Purchase Plan, or the ESPP, allowing eligible employees to authorize payroll deductions of up to 15% of their eligible compensation. An ESPP participant may purchase a maximum of 4,000 shares, or a lesser number as determined by the IRS rules, each six-month period. The offering periods generally start on the first trading day on or after February 20 and August 20 of each year. Participants in an offering period are granted the right to purchase common shares at a price per share that is 85% of the lesser of the fair market value of the shares on (1) the first day of the offering period or (2) the end of the purchase period. The number of shares reserved for the ESPP may increase each year, beginning on January 1, 2017 and continuing through and including January 1, 2036, by the lesser of: (1) 1% of the total number of shares of common stock outstanding on the first day of each year; (2) 365,411 shares of common stock; and (3) an amount determined by our board of directors.

As of December 31, 2025, the total unrecognized stock-based compensation from the ESPP was $0.3 million, which we will recognize on a straight-line basis over the weighted-average remaining service period of less than one year.

We estimate the fair value of the ESPP grant at the start of the offering period using the Black-Scholes option-pricing model with the following assumptions for the periods presented:


	Year Ended December 31,
	2025	2024	2023
Risk-free interest rate	4.1% - 4.3%	5.0% - 5.3%	5.1% - 5.6%
Expected term	0.5 Years	0.5 Years	0.5 Years
Expected volatility	53.2% - 80.6%	59.9% - 61.6%	64.7% - 85.9%