Western Digital Corporation
CH ˙ BRSE ˙ US9581021055
DETTE SYMBOL ER IKKE LÆNGERE AKTIVT
SecurityCH:12355 / Western Digital Corporation
InstitutionBnp Paribas Arbitrage, Sa
Latest Disclosed Ownership1,188,956 shares
Latest Disclosed Value $ 321,600,708
Bnp Paribas Arbitrage, Sa ownership in 12355 / Western Digital Corporation

On May 12, 2026 - Bnp Paribas Arbitrage, Sa filed a 13F-HR form disclosing ownership of 1,188,956 shares of Western Digital Corporation (CH:12355) valued at $321,600,708 USD as of March 31, 2026. The entity filed a previous 13F-HR on February 10, 2026 disclosing 1,398,080 shares of Western Digital Corporation. This represents a change in shares of -14.96% during the quarter.

Bnp Paribas Arbitrage, Sa has a history of taking positions in derivatives of the underlying security (12355) in the form of stock options. The firm currently holds call options representing 637 of underlying shares valued at $17,230,213 USD and put options representing 10,059 of underlying shares valued at $272,085,891 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.

Upgrade to unlock premium data and export to Excel .

Institutional Put/Call Ratios
(Premium Subscription Required)

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.

CH:12355 / Western Digital Corporation 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)
2026-05-12 2026-03-31 13F Western Digital Equity 958102105 1,188,956 -209,124 -14.96 321,601 33.53 0.0160
2026-02-10 2025-12-31 13F Western Digital Equity 958102105 1,398,080 -277,881 -16.58 240,847 19.70 0.1091
2025-11-13 2025-09-30 13F Western Digital Equity 958102105 1,675,961 184,861 12.40 201,216 110.88 0.1074
2025-08-14 2025-06-30 13F Western Digital Equity 958102105 1,491,100 -193,786 -11.50 95,415 40.07 0.0547
2025-05-14 2025-03-31 13F Western Digital Equity 958102105 1,684,886 349,471 26.17 68,120 -14.46 0.0401
2025-02-14 2024-12-31 13F Western Digital Equity 958102105 1,335,415 184,961 16.08 79,631 1.36 0.0446
2024-11-13 2024-09-30 13F Western Digital Equity 958102105 1,150,454 294,654 34.43 78,565 21.16 0.0528
2024-08-13 2024-06-30 13F Western Digital Equity 958102105 855,800 -207,720 -19.53 64,844 -10.65 0.0528
2024-05-01 2024-03-31 13F Western Digital Equity 958102105 1,063,520 -674,085 -38.79 72,575 -20.25 0.0637
2024-02-14 2023-12-31 13F/A-2 Western Digital Equity 958102105 1,737,605 1,299,631 296.74 90,998 355.35 0.1033
2024-02-07 2023-12-31 13F/A-1 Western Digital Equity 958102105 1,695,686 1,257,712 88,803 0.0125
2024-02-07 2023-12-31 13F Western Digital Equity 958102105 1,695,686 1,257,712 88,803 0.1028
2023-11-14 2023-09-30 13F Western Digital Equity 958102105 437,974 -12,902 -2.86 19,985 16.86 0.0257
2023-08-09 2023-06-30 13F Western Digital Equity 958102105 450,876 -4,649 -1.02 17,102 -0.34 0.0214
2023-05-12 2023-03-31 13F WESTERN DIGITAL EQUITY 958102105 455,525 278 0.06 17,160 19.47 0.0240
2023-02-14 2022-12-31 13F Western Digital Equity 958102105 455,247 63,324 16.16 14,363 12.59 0.0221
2022-11-16 2022-09-30 13F/A-1 Western Digital Equity 958102105 391,923 -33,184 -7.81 12,757 -33.06 0.0204
2022-11-15 2022-09-30 13F Western Digital Equity 958102105 391,923 -33,184 12,757 0.0031
2022-08-12 2022-06-30 13F Western Digital Equity 958102105 425,107 211,838 99.33 19,058 79.99 0.0297
2022-05-18 2022-03-31 13F/A-1 Western Digital Equity 958102105 213,269 7,601 3.70 10,589 -21.05 0.0142
2022-02-09 2021-12-31 13F WESTERN DIGITAL EQUITY 958102105 205,668 -66,691 -24.49 13,412 -12.75 0.0191
2021-11-16 2021-09-30 13F/A-1 WESTERN DIGITAL EQUITY 958102105 272,359 -109,595 -28.69 15,372 -43.45 0.0218
2021-11-12 2021-09-30 13F WESTERN DIGITAL EQUITY 958102105 329,379 -52,575 12,039 0.0000
2021-08-10 2021-06-30 13F WESTERN DIGITAL EQUITY 958102105 381,954 182,784 91.77 27,184 104.48 0.0360
2021-05-07 2021-03-31 13F WESTERN DIGITAL EQUITY 958102105 199,170 91,289 84.62 13,295 122.49 0.0195
2021-02-10 2020-12-31 13F WESTERN DIGITAL EQUITY 958102105 107,881 -221,498 -67.25 5,976 -50.37 0.0111
2020-10-30 2020-09-30 13F WESTERN DIGITAL EQUITY 958102105 329,379 1,746 0.53 12,039 -16.77 0.0172
2020-08-06 2020-06-30 13F WESTERN DIGITAL EQUITY 958102105 327,633 30,542 10.28 14,465 16.98 0.0255
2020-05-13 2020-03-31 13F WESTERN DIGITAL EQUITY 958102105 297,091 48,127 19.33 12,365 -21.75 0.0254
2020-02-12 2019-12-31 13F WESTERN DIGITAL EQUITY 958102105 248,964 71,753 40.49 15,802 49.52 0.0288
2019-11-07 2019-09-30 13F WESTERN DIGITAL EQUITY 958102105 177,211 -197,481 -52.70 10,569 -40.68 0.0188
2019-07-30 2019-06-30 13F WESTERN DIGITAL EQUITY 958102105 374,692 -222,182 -37.22 17,817 -37.89 0.0355
2019-04-25 2019-03-31 13F WESTERN DIGITAL EQUITY 958102105 596,874 87,736 17.23 28,686 52.40 0.0620
2019-02-12 2018-12-31 13F WESTERN DIGITAL EQUITY 958102105 509,138 12,904 2.60 18,823 -35.21 0.0445
2018-11-07 2018-09-30 13F WESTERN DIGITAL EQUITY 958102105 496,234 -97,368 -16.40 29,050 -36.78 0.0429
2018-07-25 2018-06-30 13F WESTERN DIGITAL EQUITY 958102105 593,602 -77,839 -11.59 45,951 -25.83 0.0765
2018-05-11 2018-03-31 13F WESTERN DIGITAL EQUITY 958102105 671,441 422,082 169.27 61,954 212.40 0.1160
2018-03-05 2017-12-31 13F/A-1 WESTERN DIGITAL EQUITY 958102105 249,359 -58,562 -19.02 19,832 -25.46 0.0352
2018-02-01 2017-12-31 13F WESTERN DIGITAL EQUITY 958102105 249,359 -58,562 19,832
2017-11-03 2017-09-30 13F WESTERN DIGITAL STOCK 958102105 307,921 -31,246 -9.21 26,604 -11.47 0.0650
2017-08-03 2017-06-30 13F WESTERN DIGITAL STOCK 958102105 339,167 28,948 9.33 30,050 17.37 0.0906
2017-05-03 2017-03-31 13F WESTERN DIGITAL STOCK 958102105 310,219 168,480 118.87 25,602 165.83 0.0676
2017-02-14 2016-12-31 13F WESTERN DIGITAL STOCK 958102105 141,739 -83,311 -37.02 9,631 -26.80 0.0451
2016-10-05 2016-09-30 13F * WESTERN DIGITAL CORP COM STOCK 958102105 225,050 85,407 61.16 13,159 99.39 0.0542
2016-07-06 2016-06-30 13F * WESTERN DIGITAL CORP COM STOCK 958102105 139,643 -208,146 -59.85 6,600 -59.83 0.0298
2016-04-22 2016-03-31 13F * WESTERN DIGITAL CORP COM STOCK 958102105 347,789 255,135 275.36 16,430 195.33 0.0695
2016-04-19 2015-12-31 13F/A-1 * WESTERN DIGITAL CORP COM STOCK 958102105 92,654 -149,458 -61.73 5,564 -71.08 0.0271
2016-02-10 2015-12-31 13F * WESTERN DIGITAL CORP COM STOCK 958102105 92,654 5,564
2015-11-13 2015-09-30 13F * WESTERN DIGITAL CORP COM STOCK 958102105 242,112 79,849 49.21 19,233 51.16 0.0482
2015-08-14 2015-06-30 13F WESTERN DIGITAL CORP COM STOCK 958102105 162,263 -101,041 -38.37 12,725 -46.90 0.0355
2015-05-15 2015-03-31 13F * WESTERN DIGITAL CORP COM STOCK 958102105 263,304 -91,536 -25.80 23,963 -38.99 0.0663
2015-03-10 2014-12-31 13F/A-1 * WESTERN DIGITAL CORP COM STOCK 958102105 354,840 107,954 43.73 39,281 63.49 0.1392
2015-02-11 2014-12-31 13F * WESTERN DIGITAL CORP COM STOCK 958102105 354,840 39,281
2014-11-12 2014-09-30 13F WESTERN DIGITAL CORP COM STOCK 958102105 246,886 87,837 55.23 24,027 63.66 0.0209
2014-08-14 2014-06-30 13F/A-1 * WESTERN DIGITAL CORP COM STOCK 958102105 159,049 -151,697 -48.82 14,680 -46.36 0.0138
2014-08-14 2014-06-30 13F WESTERN DIGITAL CORP COM STOCK 958102105 159,049 14,680
2014-05-13 2014-03-31 13F WESTERN DIGITAL STOCK 958102105 310,746 -111,732 -26.45 27,370 -22.78 0.0213
2014-04-02 2013-12-31 13F/A-1 WESTERN DIGITAL STOCK 958102105 422,478 9,984 2.42 35,446 35.53 0.0258
2014-02-12 2013-12-31 13F WESTERN DIGITAL STOCK 958102105 422,478 35,446
2013-11-13 2013-09-30 13F WESTERN DIGITAL STOCK 958102105 412,494 240,609 139.98 26,152 145.05 0.0190
2013-08-13 2013-06-30 13F WESTERN DIGITAL STOCK 958102105 171,885 171,885 10,672 0.0075
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
(%)
2026-05-12 2026-03-31 13F Western Digital Option Call 637 -64.01 17,230 -43.49 n/a n/a n/a
2026-02-10 2025-12-31 13F Western Digital Option Call 1,770 3.81 30,492 48.95 n/a n/a n/a
2025-11-13 2025-09-30 13F Western Digital Option Call 1,705 150.00 20,470 369.07 n/a n/a n/a
2025-08-14 2025-06-30 13F Western Digital Option Call 682 3.81 4,364 64.31 n/a n/a n/a
2025-05-14 2025-03-31 13F Western Digital Option Call 657 -67.57 2,656 -78.02 n/a n/a n/a
2025-02-14 2024-12-31 13F Western Digital Option Call 2,026 103.62 12,081 77.82 n/a n/a n/a
2024-11-13 2024-09-30 13F Western Digital Option Call 995 -30.52 6,795 -37.38 n/a n/a n/a
2024-08-13 2024-06-30 13F Western Digital Option Call 1,432 48.86 10,850 65.30 n/a n/a n/a
2024-05-01 2024-03-31 13F Western Digital Option Call 962 6,565 n/a n/a n/a
2023-05-12 2023-03-31 13F Western Digital Option Call 0 -100.00 0 -100.00 n/a n/a n/a
2023-02-14 2022-12-31 13F Western Digital Option Call 1,156 5.09 3,647 1.87 n/a n/a n/a
2022-11-16 2022-09-30 13F/A Western Digital Option Call 1,100 0.00 3,580 -27.40 n/a n/a n/a
2022-11-15 2022-09-30 13F Western Digital Option Call 1,100 3,580 n/a n/a n/a
2022-08-12 2022-06-30 13F Western Digital Option Call 1,100 0.00 4,931 -9.71 n/a n/a n/a
2022-05-18 2022-03-31 13F/A Western Digital Option Call 1,100 -31.25 5,462 -47.66 n/a n/a n/a
2022-02-09 2021-12-31 13F WESTERN DIGITAL OPTION Call 1,600 45.45 10,434 68.06 n/a n/a n/a
2021-11-16 2021-09-30 13F/A WESTERN DIGITAL OPTION Call 1,100 0.00 6,208 -20.69 n/a n/a n/a
2021-11-12 2021-09-30 13F WESTERN DIGITAL OPTION Call 200 731 n/a n/a n/a
2021-08-10 2021-06-30 13F WESTERN DIGITAL OPTION Call 1,100 0.00 7,829 6.62 n/a n/a n/a
2021-05-07 2021-03-31 13F WESTERN DIGITAL OPTION Call 1,100 -15.38 7,342 1.97 n/a n/a n/a
2021-02-10 2020-12-31 13F WESTERN DIGITAL OPTION Call 1,300 550.00 7,201 884.95 n/a n/a n/a
2020-10-30 2020-09-30 13F WESTERN DIGITAL OPTION Call 200 0.00 731 -17.21 n/a n/a n/a
2020-08-06 2020-06-30 13F WESTERN DIGITAL OPTION Call 200 883 n/a n/a n/a
2020-05-13 2020-03-31 13F WESTERN DIGITAL OPTION Call 0 -100.00 0 -100.00 n/a n/a n/a
2020-02-12 2019-12-31 13F WESTERN DIGITAL OPTION Call 635 -43.95 4,030 -40.36 n/a n/a n/a
2019-11-07 2019-09-30 13F WESTERN DIGITAL OPTION Call 1,133 -8.56 6,757 14.70 n/a n/a n/a
2019-07-30 2019-06-30 13F WESTERN DIGITAL OPTION Call 1,239 41.60 5,891 40.10 n/a n/a n/a
2019-04-25 2019-03-31 13F WESTERN DIGITAL OPTION Call 875 32.38 4,205 72.12 n/a n/a n/a
2019-02-12 2018-12-31 13F WESTERN DIGITAL OPTION Call 661 0.00 2,444 -36.86 n/a n/a n/a
2018-11-07 2018-09-30 13F WESTERN DIGITAL OPTION Call 661 48.21 3,869 12.08 n/a n/a n/a
2018-07-25 2018-06-30 13F WESTERN DIGITAL OPTION Call 446 3,452 n/a n/a n/a
2018-03-05 2017-12-31 13F/A WESTERN DIGITAL OPTION Call 0 -100.00 0 -100.00 n/a n/a n/a
2017-11-03 2017-09-30 13F WESTERN DIGITAL OPTION Call 350 -75.02 113 -63.52 n/a n/a n/a
2017-08-03 2017-06-30 13F WESTERN DIGITAL OPTION Call 1,401 307 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
(%)
2026-05-12 2026-03-31 13F Western Digital Option Put 10,059 -47.88 272,086 -18.17 n/a n/a n/a
2026-02-10 2025-12-31 13F Western Digital Option Put 19,300 6.78 332,481 53.21 n/a n/a n/a
2025-11-13 2025-09-30 13F Western Digital Option Put 18,075 582.59 217,008 1,180.74 n/a n/a n/a
2025-08-14 2025-06-30 13F Western Digital Option Put 2,648 -8.34 16,945 45.07 n/a n/a n/a
2025-05-14 2025-03-31 13F Western Digital Option Put 2,889 -28.15 11,680 -51.29 n/a n/a n/a
2025-02-14 2024-12-31 13F Western Digital Option Put 4,021 3.69 23,977 -9.46 n/a n/a n/a
2024-11-13 2024-09-30 13F Western Digital Option Put 3,878 17.62 26,483 6.01 n/a n/a n/a
2024-08-13 2024-06-30 13F Western Digital Option Put 3,297 27.84 24,981 41.95 n/a n/a n/a
2024-05-01 2024-03-31 13F Western Digital Option Put 2,579 247.57 17,599 353.00 n/a n/a n/a
2024-02-14 2023-12-31 13F/A Western Digital Option Put 742 162.19 3,886 200.93 n/a n/a n/a
2024-02-07 2023-12-31 13F/A Western Digital Option Put 742 3,886 n/a n/a n/a
2024-02-07 2023-12-31 13F Western Digital Option Put 742 3,886 n/a n/a n/a
2023-11-14 2023-09-30 13F Western Digital Option Put 283 0.00 1,291 20.32 n/a n/a n/a
2023-08-09 2023-06-30 13F Western Digital Option Put 283 0.00 1,073 0.66 n/a n/a n/a
2023-05-12 2023-03-31 13F WESTERN DIGITAL OPTION Put 283 -77.94 1,066 -73.66 n/a n/a n/a
2023-02-14 2022-12-31 13F Western Digital Option Put 1,283 -33.28 4,048 -35.34 n/a n/a n/a
2022-11-16 2022-09-30 13F/A Western Digital Option Put 1,923 -9.16 6,259 -34.05 n/a n/a n/a
2022-11-15 2022-09-30 13F Western Digital Option Put 1,923 6,259 n/a n/a n/a
2022-08-12 2022-06-30 13F Western Digital Option Put 2,117 -34.46 9,491 -40.82 n/a n/a n/a
2022-05-18 2022-03-31 13F/A Western Digital Option Put 3,230 -36.42 16,037 -51.59 n/a n/a n/a
2022-02-09 2021-12-31 13F WESTERN DIGITAL OPTION Put 5,080 -25.86 33,127 -14.34 n/a n/a n/a
2021-11-16 2021-09-30 13F/A WESTERN DIGITAL OPTION Put 6,852 46.98 38,673 16.56 n/a n/a n/a
2021-11-12 2021-09-30 13F WESTERN DIGITAL OPTION Put 4,161 15,208 n/a n/a n/a
2021-08-10 2021-06-30 13F WESTERN DIGITAL OPTION Put 4,662 -3.58 33,179 2.81 n/a n/a n/a
2021-05-07 2021-03-31 13F WESTERN DIGITAL OPTION Put 4,835 -6.53 32,274 12.63 n/a n/a n/a
2021-02-10 2020-12-31 13F WESTERN DIGITAL OPTION Put 5,173 24.32 28,653 88.41 n/a n/a n/a
2020-10-30 2020-09-30 13F WESTERN DIGITAL OPTION Put 4,161 63.69 15,208 35.52 n/a n/a n/a
2020-08-06 2020-06-30 13F WESTERN DIGITAL OPTION Put 2,542 51.04 11,223 60.22 n/a n/a n/a
2020-05-13 2020-03-31 13F WESTERN DIGITAL OPTION Put 1,683 5.45 7,005 -30.85 n/a n/a n/a
2020-02-12 2019-12-31 13F WESTERN DIGITAL OPTION Put 1,596 -15.60 10,130 -10.18 n/a n/a n/a
2019-11-07 2019-09-30 13F WESTERN DIGITAL OPTION Put 1,891 -37.96 11,278 -22.19 n/a n/a n/a
2019-07-30 2019-06-30 13F WESTERN DIGITAL OPTION Put 3,048 -6.56 14,493 -7.55 n/a n/a n/a
2019-04-25 2019-03-31 13F WESTERN DIGITAL OPTION Put 3,262 23.84 15,677 61.00 n/a n/a n/a
2019-02-12 2018-12-31 13F WESTERN DIGITAL OPTION Put 2,634 28.99 9,738 -18.54 n/a n/a n/a
2018-11-07 2018-09-30 13F WESTERN DIGITAL OPTION Put 2,042 315.89 11,954 214.55 n/a n/a n/a
2018-07-25 2018-06-30 13F WESTERN DIGITAL OPTION Put 491 -97.11 3,801 142.35 n/a n/a n/a
2018-05-11 2018-03-31 13F WESTERN DIGITAL OPTION Put 17,000 -13.71 1,569 0.13 n/a n/a n/a
2018-03-05 2017-12-31 13F/A WESTERN DIGITAL OPTION Put 19,700 39,300.00 1,567 9,111.76 n/a n/a n/a
2018-02-01 2017-12-31 13F WESTERN DIGITAL OPTION Put 19,700 1,567 n/a n/a n/a
2017-11-03 2017-09-30 13F WESTERN DIGITAL OPTION Put 50 -97.13 18 -97.00 n/a n/a n/a
2017-08-03 2017-06-30 13F WESTERN DIGITAL OPTION Put 1,741 1,558.10 567 77,042.45 n/a n/a n/a
2017-05-03 2017-03-31 13F WESTERN DIGITAL OPTION Put 105 5.00 1 635.00 n/a n/a n/a
2017-02-14 2016-12-31 13F WESTERN DIGITAL OPTION Put 100 0 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.