Western Digital Corporation
CH ˙ BRSE ˙ US9581021055
DETTE SYMBOL ER IKKE LÆNGERE AKTIVT
SecurityCH:12355 / Western Digital Corporation
InstitutionLMR Partners LLP
Latest Disclosed Ownership2,540 shares
Latest Disclosed Value $ 687,045
LMR Partners LLP ownership in 12355 / Western Digital Corporation

On May 15, 2026 - LMR Partners LLP filed a 13F-HR form disclosing ownership of 2,540 shares of Western Digital Corporation (CH:12355) valued at $687,045 USD as of March 31, 2026. The entity filed a previous 13F-HR on February 17, 2026 disclosing 235,742 shares of Western Digital Corporation. This represents a change in shares of -98.92% during the quarter.

LMR Partners LLP 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 0 of underlying shares valued at $0 USD and put options representing 0 of underlying shares valued at $0 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.

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)
2026-05-15 2026-03-31 13F WESTERN DIGITAL COM 958102105 2,540 -233,202 -98.92 687 -98.31 0.0015
2026-02-17 2025-12-31 13F WESTERN DIGITAL COM 958102105 235,742 -199,180 -45.80 40,611 -22.22 0.0764
2025-11-14 2025-09-30 13F WESTERN DIGITAL COM 958102105 434,922 -940,947 -68.39 52,217 -40.69 0.2302
2025-08-14 2025-06-30 13F WESTERN DIGITAL COM 958102105 1,375,869 389,500 39.49 88,042 120.78 0.6302
2025-05-15 2025-03-31 13F WESTERN DIGITAL COM 958102105 986,369 533,691 117.90 39,879 47.73 0.3730
2025-02-14 2024-12-31 13F WESTERN DIGITAL COM 958102105 452,678 395,047 685.48 26,993 585.97 0.2270
2024-11-07 2024-09-30 13F WESTERN DIGITAL COM 958102105 57,631 57,631 3,936 0.0313
2024-05-15 2024-03-31 13F WESTERN DIGITAL COM 958102105 0 -192,814 -100.00 0 -100.00
2024-02-14 2023-12-31 13F WESTERN DIGITAL COM 958102105 192,814 115,141 148.24 10,098 184.90 0.1153
2023-11-14 2023-09-30 13F WESTERN DIGITAL COM 958102105 77,673 77,673 3,544 0.0398
2023-02-14 2022-12-31 13F WESTERN DIGITAL COM 958102105 0 -123,602 -100.00 0 -100.00
2022-11-14 2022-09-30 13F WESTERN DIGITAL COM 958102105 123,602 123,602 4,023 0.0740
2021-11-15 2021-09-30 13F WESTERN DIGITAL COM 958102105 0 -341,828 -100.00 0 -100.00
2021-08-16 2021-06-30 13F WESTERN DIGITAL COM 958102105 341,828 247,937 264.07 24,328 288.19 0.3677
2021-05-17 2021-03-31 13F WESTERN DIGITAL COM 958102105 93,891 42,543 82.85 6,267 120.36 0.1561
2021-02-16 2020-12-31 13F WESTERN DIGITAL COM 958102105 51,348 51,348 2,844 0.0442
2020-11-16 2020-09-30 13F WESTERN DIGITAL COM 958102105 0 -8,186 -100.00 0 -100.00
2020-08-14 2020-06-30 13F WESTERN DIGITAL COM 958102105 8,186 2,624 47.18 361 49.17 0.0090
2020-08-14 2020-03-31 13F/A-1 WESTERN DIGITAL COM 958102105 5,562 -10,494 -65.36 242 -76.25 0.0113
2020-05-15 2020-03-31 13F WESTERN DIGITAL COM 958102105 5,562 -10,494 242 251.4993
2020-02-14 2019-12-31 13F WESTERN DIGITAL COM 958102105 16,056 16,056 1,019 0.0017
2019-08-14 2019-06-30 13F WESTERN DIGITAL COM 958102105 0 -6,903 -100.00 0 -100.00
2019-05-15 2019-03-31 13F WESTERN DIGITAL COM 958102105 6,903 6,903 332 0.0169
2019-02-14 2018-12-31 13F WESTERN DIGITAL COM 958102105 0 -17,737 -100.00 0 -100.00
2018-11-14 2018-09-30 13F WESTERN DIGITAL COM 958102105 17,737 11,253 173.55 1,038 106.77 0.0660
2018-08-03 2018-06-30 13F WESTERN DIGITAL COM 958102105 6,484 3,686 131.74 502 125.11 0.0260
2018-05-04 2018-03-31 13F WESTERN DIGITAL COM 958102105 2,798 0 0.00 223 0.00 0.0229
2018-01-30 2017-12-31 13F WESTERN DIGITAL COM 958102105 2,798 -2,047 -42.25 223 -46.65 0.0229
2017-11-09 2017-09-30 13F WESTERN DIGITAL COM 958102105 4,845 -5,478 -53.07 418 -54.32 0.0452
2017-08-03 2017-06-30 13F WESTERN DIGITAL COM 958102105 10,323 3,188 44.68 915 55.35 0.0574
2017-05-11 2017-03-31 13F WESTERN DIGITAL COM 958102105 7,135 7,135 589 0.0566
2015-11-05 2015-09-30 13F WESTERN DIGITAL COM 958102105 0 -10,046 -100.00 0 -100.00
2015-08-10 2015-06-30 13F WESTERN DIGITAL COM 958102105 10,046 -4,784 -32.26 788 -41.59 0.0963
2015-04-20 2015-03-31 13F WESTERN DIGITAL COM 958102105 14,830 -10,794 -42.12 1,349 -52.45 0.1865
2015-01-20 2014-12-31 13F WESTERN DIGITAL COM 958102105 25,624 25,624 0.00 2,837 0.3708
2014-10-20 2014-09-30 13F WESTERN DIGITAL COM 958102105 0 -47,798 -100.00 0 -100.00
2014-07-10 2014-06-30 13F WESTERN DIGITAL COM 958102105 47,798 47,798 4,411 0.3669
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 WESTERN DIGITAL COM Call 0 -100.00 0 -100.00 n/a n/a n/a
2026-02-17 2025-12-31 13F WESTERN DIGITAL COM Call 369,000 -14.46 63,568 22.73 n/a n/a n/a
2025-11-14 2025-09-30 13F WESTERN DIGITAL COM Call 431,400 51,794 n/a n/a n/a
2025-05-15 2025-03-31 13F WESTERN DIGITAL COM Call 0 -100.00 0 -100.00 n/a n/a n/a
2025-02-14 2024-12-31 13F WESTERN DIGITAL COM Call 378,400 2,139.05 22,564 1,855.20 n/a n/a n/a
2024-11-07 2024-09-30 13F WESTERN DIGITAL COM Call 16,900 -56.78 1,154 -61.04 n/a n/a n/a
2024-08-14 2024-06-30 13F WESTERN DIGITAL COM Call 39,100 -63.93 2,963 -59.96 n/a n/a n/a
2024-05-15 2024-03-31 13F WESTERN DIGITAL COM Call 108,400 -13.21 7,397 13.09 n/a n/a n/a
2024-02-14 2023-12-31 13F WESTERN DIGITAL COM Call 124,900 203.89 6,541 248.85 n/a n/a n/a
2023-11-14 2023-09-30 13F WESTERN DIGITAL COM Call 41,100 1,875 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 WESTERN DIGITAL COM Put 0 -100.00 0 -100.00 n/a n/a n/a
2026-02-17 2025-12-31 13F WESTERN DIGITAL COM Put 29,200 -53.21 5,030 -32.85 n/a n/a n/a
2025-11-14 2025-09-30 13F WESTERN DIGITAL COM Put 62,400 7,492 n/a n/a n/a
2025-05-15 2025-03-31 13F WESTERN DIGITAL COM Put 0 -100.00 0 -100.00 n/a n/a n/a
2025-02-14 2024-12-31 13F WESTERN DIGITAL COM Put 583,300 -3.23 34,782 -15.51 n/a n/a n/a
2024-11-07 2024-09-30 13F WESTERN DIGITAL COM Put 602,800 3.82 41,165 -6.43 n/a n/a n/a
2024-08-14 2024-06-30 13F WESTERN DIGITAL COM Put 580,600 3.53 43,992 14.96 n/a n/a n/a
2024-05-15 2024-03-31 13F WESTERN DIGITAL COM Put 560,800 3.03 38,269 34.25 n/a n/a n/a
2024-02-14 2023-12-31 13F WESTERN DIGITAL COM Put 544,300 6,379.76 28,505 7,342.30 n/a n/a n/a
2023-11-14 2023-09-30 13F WESTERN DIGITAL COM Put 8,400 383 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.