Seagate Technology Holdings plc

The full register, from 13F filings

The Register tab above is hand research: a dozen holders, each traced to the filing it came from. This asks the same question of the whole market for the quarter ended 31-mar-2026, where 1,434 managers reported a position. Broad where the research is deep, and shallow in the ways a 13F always is.

Built from 13F filings, which report US listed, long, US custodied positions only. A register from this source is a floor rather than a level: a holder's true position can be far larger, as BlackRock's ASML stake shows at 1.28m shares in a 13F against 26.3m in its 13G/A. Holdings held through derivatives, outside US custody, or below a manager's reporting obligation do not appear. Where a holder is marked as a family, its total sums several separate filing entities and describes something no single filing describes; the constituent entities and their share counts are listed so the total can be checked. That roll-up can legitimately exceed the family's own Schedule 13G, because a 13G is filed by one legal entity: Vanguard reports Alphabet through ten advisory entities, and The Vanguard Group Inc itself reported zero after its January 2026 disaggregation.

What a reader needs to know to read these numbers

• Seagate Technology Holdings plc is an Irish-domiciled public limited company; its listed instrument is ordinary shares, par value $0.00001 (Section 12(b) registration: 'Ordinary Shares, par value $0.00001 per share'), not common stock. CUSIP G7997R103 carries a G-prefix reflecting the Irish domicile, the same pattern seen on Trane Technologies plc (CUSIP G8994E103), and is expected, not an error. Authorized share capital also includes 100,000,000 preferred shares, par value $0.00001, none of which were issued or outstanding as of 3 Jul 2026 per the FY2026 10-K equity note.
• Shares outstanding. The FY2026 10-K (period ended 3 Jul 2026, filed 4 Aug 2026, the most recent SEC filing) is used because Seagate's fiscal year ends in late June/early July, making the 10-K more current than the last 10-Q (period ended 3 Apr 2026, filed 29 Apr 2026). The cover page states 226,644,518 ordinary shares outstanding as of 31 Jul 2026; the separately disclosed balance-sheet figure of 226,791,724 shares outstanding as of 3 Jul 2026 (fiscal year end) is close but from an earlier date, so the cover page figure is used as shares_outstanding. Market cap ($225.46bn) and price ($994.79) are stockanalysis.com's closing figures for 17 Aug 2026; cross-check, 226,644,518 x $994.79 implies approximately $225.46bn, consistent with the reported market cap.
• Holdings. The FY2026 10-K (filed 4 Aug 2026, covering the year ended 3 Jul 2026) was searched for 'equity method', 'unconsolidated', 'joint venture', 'strategic investment', 'non-marketable', 'noncontrolling interest', 'equity investment', 'affiliate', 'investment in', and 'investee'. 'Unconsolidated' and 'non-marketable' and 'noncontrolling interest' returned no hits. The Company's own accounting policy note ('Equity Investments') states it enters into strategic investments accounted for either under the equity method or a measurement alternative, both included within a combined 'Other assets, net' balance sheet line, with no individual investee named anywhere in the document. The measurement-alternative investments' aggregate carrying value was disclosed as $19 million at 3 Jul 2026 and $26 million at 27 Jun 2025; the equity-method investments were separately described only as 'immaterial' with no dollar figure. Per the no-combined-balance rule, neither figure is attributable to any single investee, so the holdings array is left empty by design rather than assigning the combined balance to a guessed target.
• Register: the Vanguard rule. Vanguard Group Inc (CIK 0000102909) filed Form 13F-NT (notice, no holdings) for the quarter ended 30 June 2026; its filing folder was checked directly and contains only primary_doc.xml, no information table. Its Seagate position is instead reported by two successor entities, Vanguard Capital Management LLC and Vanguard Portfolio Management LLC, which are summed into the single Vanguard row per project rule 7.
• Register: Capital Group. All three Capital Group-family 13F filers named in the verified CIK list were checked individually for Q2 2026 and all three hold Seagate: Capital World Investors (CIK 0001422849, 151,440 shares), Capital International Investors (CIK 0001562230, 1,032,054 shares), and Capital Research Global Investors (CIK 0001422848, 4,326,781 shares), summed to 5,510,275 shares as one 'Capital Group' row naming all three entities. This is NOT the Vanguard successor case: these are three co-equal sibling filers reporting simultaneously (not a parent-filed-NT-so-successors-are-the-position substitution), so the row is a straightforward sum, not is_aggregate.
• Thousands-convention check. Implied price per share (value_usd / shares) for every Q2 2026 13F register row clusters between approximately $962 and $969, consistent with Seagate's ~$965 closing price around the 30 Jun 2026 valuation date used by 13F filers; no row is off by a factor of roughly 1,000, so no thousands-convention rescaling was needed among the filers checked here. T. Rowe Price was not checked for this company (it ranked outside the top 12 by shares in the Q1 2026 project register snapshot: 27,454,827 combined at rank 1 was Vanguard, and T. Rowe Price did not appear in the top 20 holders listed).
• Sanders Capital reconciliation. Seagate's September 2025 proxy cites a Schedule 13G/A reporting Sanders Capital, LLC at 18,902,646 shares (8.88%) as of 31 Mar 2025. The project's Q1 2026 13F register snapshot (31 Mar 2026, not used directly per the brief) showed Sanders Capital at 12,897,201 shares. Sanders Capital's own Q2 2026 Form 13F-HR, read directly, shows a further reduction to 3,487,219 shares. All three figures are filed; the register uses the most current (Q2 2026) figure, and the large step-down is recorded here rather than silently overwritten.
• Register versus proxy 13G dates. The September 2025 proxy's 5%-holder table cites Schedule 13G/A filing dates of 22 Jul 2025 (JPMorgan), 23 Apr 2025 (BlackRock), 14 May 2025 (Sanders Capital), 31 Jan 2025 (Vanguard) and 13 Feb 2025 (Capital Research Global Investors, a Schedule 13G). EDGAR's own filing index for CIK 0001137789, checked directly via the recent-filings feed, shows no Schedule 13G, 13G/A, 13D or 13D/A filed for Seagate since 12 Nov 2024 (two 13G/A amendments that date). This mirrors an identical unresolved discrepancy documented in the Trane Technologies reference file for the same CIK-lookup method; not resolved within the time budget. The register uses each manager's own fresher Q2 2026 Form 13F-HR instead of these stale proxy-cited 13G figures.
• Insider ownership. The most recent DEF 14A on file is dated 9 Sep 2025 (record date 27 Aug 2025, ownership table as of 22 Aug 2025); Seagate's FY2026 proxy (for the fiscal year ended 3 Jul 2026) had not yet been filed as of 17 Aug 2026. CEO William D. Mosley holds 965,668 shares (0.45% of the proxy's then-outstanding share count); all 17 named executive officers, directors and director nominees as a group hold 1,684,244 shares (0.79%). The proxy notes no dual-class structure; each ordinary share carries one vote.
• Self-gate check: summing the twelve non-insider register rows (Vanguard combined, BlackRock, State Street, FMR, Capital Group combined, JPMorgan, Geode, Sanders Capital, Norges Bank, Bank of America, Northern Trust, Franklin) plus the Mosley row at full value plus the insider group row reduced by Mosley's rolled-up shares gives 14 register rows, 85,810,780 shares against 226,644,518 shares outstanding, or 37.86%, within the expected 25 to 45 percent range.