Our stock plans include the Alphabet Amended and Restated 2012 Stock Plan, the Alphabet 2021 Stock Plan and Other Bet stock-based plans. Under our stock plans, RSUs and other types of awards may be granted. An RSU award is an agreement to issue shares of our Class C stock at the time the award vests. RSUs generally vest over four years contingent upon employment on the vesting date.

As of December 31, 2021, there were 37,479,707 shares of Class C stock reserved for future issuance under the Alphabet 2021 Stock Plan.

For the years ended December 31, 2019, 2020, and 2021, total stock-based compensation expense was $11.7 billion, $13.4 billion, and $15.7 billion, including amounts associated with awards we expect to settle in Alphabet stock of $10.8 billion, $12.8 billion, and $15.0 billion, respectively.

For the years ended December 31, 2019, 2020, and 2021, we recognized tax benefits on total stock-based compensation expense, which are reflected in the provision for income taxes in the Consolidated Statements of Income, of $1.8 billion, $2.7 billion, and $3.1 billion, respectively.

For the years ended December 31, 2019, 2020, and 2021, tax benefit realized related to awards vested or exercised during the period was $2.2 billion, $3.6 billion, and $5.9 billion, respectively. These amounts do not include the indirect effects of stock-based awards, which primarily relate to the R&D tax credit.

The following table summarizes the activities for unvested Alphabet RSUs for the year ended December 31, 2021:


	Unvested Restricted Stock Units
	Number of Shares	Weighted- Average Grant-Date Fair Value
Unvested as of December 31, 2020	19,288,793	$	1,262.13
Granted	10,582,700	$	1,949.16
Vested	(11,209,486)	$	1,345.98
Forfeited/canceled	(1,767,294)	$	1,425.48
Unvested as of December 31, 2021	16,894,713	$	1,626.13

The weighted-average grant-date fair value of RSUs granted during the years ended December 31, 2019 and 2020 was $1,092.36 and $1,407.97, respectively. Total fair value of RSUs, as of their respective vesting dates, during the years ended December 31, 2019, 2020, and 2021 were $15.2 billion, $17.8 billion, and $28.8 billion, respectively.

As of December 31, 2021, there was $25.8 billion of unrecognized compensation cost related to unvested employee RSUs. This amount is expected to be recognized over a weighted-average period of 2.5 years.

We have two 401(k) Savings Plans that qualify as deferred salary arrangements under Section 401(k) of the Internal Revenue Code. Under these 401(k) Plans, matching contributions are based upon the amount of the employees’ contributions subject to certain limitations. We recognized expense of approximately $724 million, $855 million, and $916 million for the years ended December 31, 2019, 2020, and 2021, respectively.