Magnite, Inc.
US ˙ NasdaqGS ˙ US55955D1000

SecurityMGNI / Magnite, Inc.
InstitutionCitadel Advisors Llc
ManagerKen Griffin
Latest Disclosed Ownership1,052,908 shares
Latest Disclosed Value $ 12,508,547
Citadel Advisors Llc ownership in MGNI / Magnite, Inc.

On May 15, 2026 - Citadel Advisors Llc filed a 13F-HR form disclosing ownership of 1,052,908 shares of Magnite, Inc. (US:MGNI) valued at $12,508,547 USD as of March 31, 2026. The entity filed a previous 13F-HR on February 17, 2026 disclosing 544,318 shares of Magnite, Inc.. This represents a change in shares of 93.44% during the quarter. The current value of the position is $15,456,689 USD.

Citadel Advisors Llc has a history of taking positions in derivatives of the underlying security (MGNI) in the form of stock options. The firm currently holds call options representing 104,600 of underlying shares valued at $1,242,648 USD and put options representing 1,040,000 of underlying shares valued at $12,355,200 USD .

Note: prior versions of this page mistakenly stated that the share values represented the number of options, not the number of underlying shares. For more information on the data backing these reports, please see the SEC document Frequently Asked Questions About Form 13F.

Institutional Ownership: 13F and NPORT Filings

The Security and Class in the table below are shown exactly as filed by the investor. We do our best to track continuity of investments through acquisitions, and this will be reflected in the table as changes in names. In addition to descriptive data, performance of the investment is shown over time. To calculate quarterly performance, we first calculate cost basis of the shares purchased during the quarter, then use that to calculate gross profit. Quarterly return is Gross Profit / Starting Portfolio value.

Note that cost basis is calculated and stored in thousands, so small quarterly changes in shares frequently result in a cost basis of zero.

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Institutional Put/Call Ratios
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In addition to reporting standard equity and debt issues, institutions with more than 100MM assets under management must also disclose their put and call option holdings. Since put options generally indicate negative sentiment, and call options indicate positive sentiment, we can get a sense of the overall institutional sentiment by plotting the ratio of puts to calls. The chart to the right plots the historical put/call ratio for this instrument.

Using Put/Call Ratio as an indicator of investor sentiment overcomes one of the key deficiencies of using total institutional ownership, which is that a significant amount of assets under management are invested passively to track indices. Passively-managed funds do not typically buy options, so the put/call ratio indicator more closely tracks the sentiment of actively-managed funds.

MGNI / Magnite, Inc. Historical Put/Call Ratio
Disclosed Equity Positions (from 13F/NPORT Filings)
File
Date
Effective
Date
Form Security Class ID Avg Price
Paid (Est)
Reported
Shares
ΔShares ΔShares
(%)
Reported
Value
(x1000)
ΔValue
(%)
Alloc
(%)
ΔAlloc ΔAlloc (%) Cost Basis
(x1000)
Unrealized
Gain/Loss
(x1000)
2026-05-15 2026-03-31 13F MAGNITE COM 55955D100 1,052,908 508,590 93.44 12,509 41.59 0.0018
2026-02-17 2025-12-31 13F MAGNITE COM 55955D100 544,318 374,757 221.02 8,834 139.21 0.0013
2025-11-14 2025-09-30 13F MAGNITE COM 55955D100 169,561 -665,541 -79.70 3,693 -81.67 0.0006
2025-08-14 2025-06-30 13F MAGNITE COM 55955D100 835,102 242,173 40.84 20,143 197.74 0.0035
2025-05-15 2025-03-31 13F MAGNITE COM 55955D100 592,929 282,690 91.12 6,765 36.97 0.0013
2025-02-14 2024-12-31 13F MAGNITE COM 55955D100 310,239 -392,269 -55.84 4,939 -49.23 0.0009
2024-11-14 2024-09-30 13F MAGNITE COM 55955D100 702,508 413,049 142.70 9,730 152.96 0.0019
2024-08-14 2024-06-30 13F MAGNITE COM 55955D100 289,459 -127,307 -30.55 3,847 -14.15 0.0008
2024-05-15 2024-03-31 13F MAGNITE COM 55955D100 416,766 36,307 9.54 4,480 26.09 0.0009
2024-02-14 2023-12-31 13F MAGNITE COM 55955D100 380,459 -173,292 -31.29 3,553 -14.90 0.0007
2023-11-14 2023-09-30 13F MAGNITE COM 55955D100 553,751 263,525 90.80 4,175 5.40 0.0009
2023-08-14 2023-06-30 13F MAGNITE COM 55955D100 290,226 -574,635 -66.44 3,962 -50.54 0.0008
2023-05-15 2023-03-31 13F MAGNITE COM 55955D100 864,861 225,010 35.17 8,009 18.18 0.0018
2023-02-14 2022-12-31 13F MAGNITE COM 55955D100 639,851 -224,178 -25.95 6,776 19.36 0.0016
2022-11-14 2022-09-30 13F MAGNITE COM 55955D100 864,029 -608,372 -41.32 5,677 -56.58 0.0013
2022-08-15 2022-06-30 13F MAGNITE COM 55955D100 1,472,401 441,022 42.76 13,075 -4.04 0.0034
2022-05-16 2022-03-31 13F MAGNITE COM 55955D100 1,031,379 39,217 3.95 13,625 -21.53 0.0028
2022-02-14 2021-12-31 13F MAGNITE COM 55955D100 992,162 -290,568 -22.65 17,363 -51.66 0.0035
2021-11-15 2021-09-30 13F MAGNITE Cmn 55955D100 1,282,730 -223,707 -14.85 35,917 -29.54 0.0075
2021-08-16 2021-06-30 13F MAGNITE COM 55955D100 1,506,437 777,711 106.72 50,978 68.12 0.0114
2021-05-21 2021-03-31 13F/A-1 MAGNITE COM 55955D100 728,726 431,981 145.57 30,323 232.74 0.0074
2021-05-17 2021-03-31 13F MAGNITE COM 55955D100 728,726 431,981 30,323 0.0074
2021-02-16 2020-12-31 13F MAGNITE COM 55955D100 296,745 -91,938 -23.65 9,113 237.64 0.0024
2020-11-16 2020-09-30 13F MAGNITE COM 55955D100 388,683 388,683 2,699 0.0008
Disclosed Call Options
File
Date
Effective
Date
Form Security Class ID Opt Avg Share
Price
Shares ΔShares
(%)
Value
(x1000)
ΔValue
(%)
Prior Allocation
(%)
Allocation
(%)
ΔAllocation
(%)
Cost Basis
(x1000)
Profit
(x1000)
Return
(%)
2026-05-15 2026-03-31 13F MAGNITE COM Call 104,600 -76.13 1,243 -82.53 n/a n/a n/a
2026-02-17 2025-12-31 13F MAGNITE COM Call 438,200 32.79 7,112 -1.06 n/a n/a n/a
2025-11-14 2025-09-30 13F MAGNITE COM Call 330,000 125.41 7,187 103.54 n/a n/a n/a
2025-08-14 2025-06-30 13F MAGNITE COM Call 146,400 -34.14 3,531 39.24 n/a n/a n/a
2025-05-15 2025-03-31 13F MAGNITE COM Call 222,300 -36.36 2,536 -54.39 n/a n/a n/a
2025-02-14 2024-12-31 13F MAGNITE COM Call 349,300 -30.25 5,561 -19.84 n/a n/a n/a
2024-11-14 2024-09-30 13F MAGNITE COM Call 500,800 89.48 6,936 97.49 n/a n/a n/a
2024-08-14 2024-06-30 13F MAGNITE COM Call 264,300 63.05 3,513 101.61 n/a n/a n/a
2024-05-15 2024-03-31 13F MAGNITE COM Call 162,100 -40.58 1,743 -31.61 n/a n/a n/a
2024-02-14 2023-12-31 13F MAGNITE COM Call 272,800 -17.01 2,548 2.78 n/a n/a n/a
2023-11-14 2023-09-30 13F MAGNITE COM Call 328,700 -27.63 2,478 -60.03 n/a n/a n/a
2023-08-14 2023-06-30 13F MAGNITE COM Call 454,200 82.48 6,200 169.05 n/a n/a n/a
2023-05-15 2023-03-31 13F MAGNITE COM Call 248,900 -27.94 2,305 -37.00 n/a n/a n/a
2023-02-14 2022-12-31 13F MAGNITE COM Call 345,400 75.06 3,658 182.18 n/a n/a n/a
2022-11-14 2022-09-30 13F MAGNITE COM Call 197,300 46.69 1,296 8.54 n/a n/a n/a
2022-08-15 2022-06-30 13F MAGNITE COM Call 134,500 -3.65 1,194 -35.25 n/a n/a n/a
2022-05-16 2022-03-31 13F MAGNITE COM Call 139,600 -16.31 1,844 -36.83 n/a n/a n/a
2022-02-14 2021-12-31 13F MAGNITE COM Call 166,800 -5.50 2,919 -40.93 n/a n/a n/a
2021-11-15 2021-09-30 13F MAGNITE Cmn Call 176,500 -24.60 4,942 -37.62 n/a n/a n/a
2021-08-16 2021-06-30 13F MAGNITE COM Call 234,100 -62.96 7,922 -69.88 n/a n/a n/a
2021-05-21 2021-03-31 13F/A MAGNITE COM Call 632,100 84.88 26,302 150.50 n/a n/a n/a
2021-05-17 2021-03-31 13F MAGNITE COM Call 632,100 26,302 n/a n/a n/a
2021-02-16 2020-12-31 13F MAGNITE COM Call 341,900 596.33 10,500 2,979.18 n/a n/a n/a
2020-11-16 2020-09-30 13F MAGNITE COM Call 49,100 341 n/a n/a n/a
Disclosed Put Options
File
Date
Effective
Date
Form Security Class ID Opt Avg Share Price Shares ΔShares
(%)
Value
(x1000)
ΔValue
(%)
Prior Allocation
(%)
Allocation
(%)
ΔAllocation
(%)
Cost Basis
(x1000)
Profit
(x1000)
Return
(%)
2026-05-15 2026-03-31 13F MAGNITE COM Put 1,040,000 36.81 12,355 0.14 n/a n/a n/a
2026-02-17 2025-12-31 13F MAGNITE COM Put 760,200 55.43 12,338 15.83 n/a n/a n/a
2025-11-14 2025-09-30 13F MAGNITE COM Put 489,100 -22.96 10,653 -30.44 n/a n/a n/a
2025-08-14 2025-06-30 13F MAGNITE COM Put 634,900 74.33 15,314 268.54 n/a n/a n/a
2025-05-15 2025-03-31 13F MAGNITE COM Put 364,200 84.50 4,156 32.24 n/a n/a n/a
2025-02-14 2024-12-31 13F MAGNITE COM Put 197,400 63.41 3,143 87.81 n/a n/a n/a
2024-11-14 2024-09-30 13F MAGNITE COM Put 120,800 63.02 1,673 70.02 n/a n/a n/a
2024-08-14 2024-06-30 13F MAGNITE COM Put 74,100 76.43 985 118.18 n/a n/a n/a
2024-05-15 2024-03-31 13F MAGNITE COM Put 42,000 -5.41 452 8.94 n/a n/a n/a
2024-02-14 2023-12-31 13F MAGNITE COM Put 44,400 -9.94 415 11.59 n/a n/a n/a
2023-11-14 2023-09-30 13F MAGNITE COM Put 49,300 -45.52 372 -69.96 n/a n/a n/a
2023-08-14 2023-06-30 13F MAGNITE COM Put 90,500 -34.28 1,235 -3.14 n/a n/a n/a
2023-05-15 2023-03-31 13F MAGNITE COM Put 137,700 71.27 1,275 49.82 n/a n/a n/a
2023-02-14 2022-12-31 13F MAGNITE COM Put 80,400 36.97 851 120.47 n/a n/a n/a
2022-11-14 2022-09-30 13F MAGNITE COM Put 58,700 -44.62 386 -58.98 n/a n/a n/a
2022-08-15 2022-06-30 13F MAGNITE COM Put 106,000 -21.66 941 -47.34 n/a n/a n/a
2022-05-16 2022-03-31 13F MAGNITE COM Put 135,300 -20.92 1,787 -40.31 n/a n/a n/a
2022-02-14 2021-12-31 13F MAGNITE COM Put 171,100 -8.50 2,994 -42.82 n/a n/a n/a
2021-11-15 2021-09-30 13F MAGNITE Cmn Put 187,000 -36.35 5,236 -47.33 n/a n/a n/a
2021-08-16 2021-06-30 13F MAGNITE COM Put 293,800 -7.76 9,942 -24.98 n/a n/a n/a
2021-05-21 2021-03-31 13F/A MAGNITE COM Put 318,500 113.04 13,253 188.67 n/a n/a n/a
2021-05-17 2021-03-31 13F MAGNITE COM Put 318,500 13,253 n/a n/a n/a
2021-02-16 2020-12-31 13F MAGNITE COM Put 149,500 106.21 4,591 810.91 n/a n/a n/a
2020-11-16 2020-09-30 13F MAGNITE COM Put 72,500 504 n/a n/a n/a
Legend
Shares
The total number of shares held by the institution at the end of the reporting period (the effective date). This is provided in the filing.
Value
The total value of the shares as of the effective date. This is provided in the filing.
Avg. Share Price
The weighted average share price of the shares held by the institution. We use FIFO accounting to determine this price
Class
This is the security class as indicated by the filer. There are a variety of values for this field. Common values include "EC" = equity common, "EP" - equity preferred
Allocation (%)
The percent of the institution's portfolio that this position represents. This is provided in NPORT filings. For 13F filings, we calculate it.
Change in Allocation
The change in allocation from the prior reporting period. This is calculated as current allocation - prior allocation.
Change in Allocation (%)
The percent change in allocation from the prior reporting period. This is calculated as (current allocation - prior allocation) / prior allocation.
Cost Basis
The total cost of the shares held. This is calculated as reported shares * avg. share price
Unrealized Gain/Loss
This is the market value of the position as of the effective date minus the cost basis.