| Stock-Based Compensation Stock-Based Compensation Expense
The following table summarizes total stock-based compensation expense (in millions): | | | | | | | | | | | | | | | Three Months Ended
March 31, | | | | | 2023 | 2024 | | Operations and support | | | | $ | 15 | | $ | 19 | | | Product development | | | | 149 | | 185 | | | Sales and marketing | | | | 28 | | 35 | | | General and administrative | | | | 48 | | 56 | | | | | | | | | Stock-based compensation expense | | | | $ | 240 | | $ | 295 | |
Stock Option and Restricted Stock Unit Activity
A summary of stock option and restricted stock unit (“RSU”) activity under the Company’s equity incentive plans was as follows (in millions, except per share amounts): | | | | | | | | | | | | | | | | | | | | | | | | | | | Outstanding Stock Options | | Outstanding RSUs | | | Shares
Available for
Grant | | Number of
Shares | Weighted-
Average
Exercise
Price | | Number of
Shares | Weighted-
Average
Grant
Date Fair
Value | | As of December 31, 2023 | 134 | | | 7 | | $ | 71.76 | | | 30 | | $ | 85.35 | | | Granted | (7) | | | — | | — | | | 7 | | 166.17 | | | Increase in shares available for grant | 13 | | | — | | — | | | — | | — | | Options exercised/RSUs vested(1) | 1 | | | (1) | | 42.12 | | | (2) | | 109.14 | | | | | | | | | | | As of March 31, 2024 | 141 | | | 6 | | $ | 80.12 | | | 35 | | $ | 100.12 | |
(1)RSUs vested are net of shares withheld for taxes. | | | | | | | | | | | | | | | | Number of
Shares | Weighted-
Average
Exercise
Price | Weighted- Average Remaining Contractual Life (Years) | Aggregate
Intrinsic
Value | | Options outstanding as of March 31, 2024 | 6 | | $ | 80.12 | | 5.87 | $ | 541 | | | Options exercisable as of March 31, 2024 | 5 | | $ | 66.85 | | 5.12 | $ | 484 | |
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