As of August 04, 2026, the three largest insider holders of STX are Holdings, L.P. Valueact (Director, 13.44Mn shares), William D Mosley (Ceo, 355.59K shares), Stephen J Luczo (Executive Chairman Cob, 225.94K shares).
| # | Insider | Position | Direct | Indirect | Total | Share of Insiders | Last Filed |
|---|---|---|---|---|---|---|---|
| 1 | Holdings, L.P. Valueact | Director, Other | 0 | 13,437,070 | 13,437,070 | 93.5% | 22 Feb, 2022 |
| 2 | William D Mosley | Ceo | 355,591 | 0 | 355,591 | 2.5% | 02 Apr, 2026 |
| 3 | Stephen J Luczo | Executive Chairman Cob | 0 | 225,941 | 225,941 | 1.6% | 08 Mar, 2022 |
| 4 | Gianluca Romano | Evp Cfo | 65,335 | 0 | 65,335 | 0.5% | 12 Mar, 2026 |
| 5 | Edward J Zander | Director | 0 | 41,357 | 41,357 | 0.3% | 22 Oct, 2021 |
| 6 | Ravi Naik | Evp, Lyve Storage Services | 38,857 | 0 | 38,857 | 0.3% | 23 Mar, 2023 |
| 7 | Jeffrey D. Nygaard | Evp, Operations And Technology | 30,360 | 0 | 30,360 | 0.2% | 02 Feb, 2023 |
| 8 | Richard L Clemmer | Director | 29,704 | 0 | 29,704 | 0.2% | 21 Oct, 2025 |
| 9 | Katherine Schuelke | Svp, Clo Corporate Secretary | 29,063 | 0 | 29,063 | 0.2% | 12 Dec, 2023 |
| 10 | John Christopher Morris | Evp Cto | 17,580 | 0 | 17,580 | 0.1% | 16 Mar, 2026 |
| 11 | Jeffrey D. Fochtman | Svp, Business Marketing | 14,736 | 0 | 14,736 | 0.1% | 14 Sep, 2022 |
| 12 | Dylan G. Haggart | Director | 14,515 | 0 | 14,515 | 0.1% | 21 Oct, 2025 |
| 13 | Judy Bruner | Director | 0 | 14,314 | 14,314 | 0.1% | 21 Oct, 2025 |
| 14 | Prat Bhatt | Director | 13,869 | 0 | 13,869 | 0.1% | 21 Oct, 2025 |
| 15 | Michael R Cannon | Director | 13,439 | 0 | 13,439 | 0.1% | 21 Oct, 2025 |
| 16 | Ban Seng Teh | Evp Chief Commercial Officer | 11,248 | 0 | 11,248 | 0.1% | 12 Mar, 2026 |
| 17 | Shankar Arumugavelu | Director | 7,626 | 0 | 7,626 | 0.1% | 12 Nov, 2025 |
| 18 | Robert A Bruggeworth | Director | 6,591 | 0 | 6,591 | 0.0% | 22 Oct, 2024 |
| 19 | Yolanda Lee Conyers | Director | 4,851 | 0 | 4,851 | 0.0% | 03 Mar, 2026 |
| 20 | Mark Adams | Director | 2,046 | 0 | 2,046 | 0.0% | 21 Oct, 2025 |
| 21 | Kian Fatt Chong | Evp Global Operations | 1,259 | 0 | 1,259 | 0.0% | 12 Mar, 2026 |
| 22 | Thomas A Szlosek | Director | 357 | 0 | 357 | 0.0% | 12 Nov, 2025 |
| 23 | James Ci Lee | Evp Clo | 257 | 0 | 257 | 0.0% | 28 Jan, 2026 |
| 24 | Jay L Geldmacher | Director | 223 | 0 | 223 | 0.0% | 02 Feb, 2026 |
Each row is that insider’s most recently reported position, from Form 4 filings over the last 60 months — which is why this total does not tie to the quarterly series above, where a quarter counts only the insiders who filed in it. Shares held through a fund or institutional portfolio are counted on the institutional ownership page instead.
| Date | Insider | Position | Transaction | Shares | Price | Value | Shares Held After | Ownership |
|---|---|---|---|---|---|---|---|---|
| 01 Apr, 2026 | William D Mosley | Ceo | Disposed S | 100 | $399.05 | $39.91K | 375,491 | Direct |
| 01 Apr, 2026 | William D Mosley | Ceo | Disposed S | 200 | $400.34 | $80.07K | 375,291 | Direct |
| 01 Apr, 2026 | William D Mosley | Ceo | Disposed S | 100 | $404.06 | $40.41K | 375,191 | Direct |
| 01 Apr, 2026 | William D Mosley | Ceo | Disposed S | 100 | $407.48 | $40.75K | 375,091 | Direct |
| 01 Apr, 2026 | William D Mosley | Ceo | Disposed S | 200 | $409.18 | $81.84K | 374,891 | Direct |
| 01 Apr, 2026 | William D Mosley | Ceo | Disposed S | 100 | $410.83 | $41.08K | 374,791 | Direct |
| 01 Apr, 2026 | William D Mosley | Ceo | Disposed S | 300 | $412.28 | $123.68K | 374,491 | Direct |
| 01 Apr, 2026 | William D Mosley | Ceo | Disposed S | 300 | $413.97 | $124.19K | 374,191 | Direct |
| 01 Apr, 2026 | William D Mosley | Ceo | Disposed S | 800 | $415.23 | $332.19K | 373,391 | Direct |
| 01 Apr, 2026 | William D Mosley | Ceo | Disposed S | 1,100 | $416.56 | $458.22K | 372,291 | Direct |
| 01 Apr, 2026 | William D Mosley | Ceo | Disposed S | 808 | $417.45 | $337.30K | 371,483 | Direct |
| 01 Apr, 2026 | William D Mosley | Ceo | Disposed S | 1,092 | $418.79 | $457.31K | 370,391 | Direct |
| 01 Apr, 2026 | William D Mosley | Ceo | Disposed S | 1,500 | $419.94 | $629.90K | 368,891 | Direct |
| 01 Apr, 2026 | William D Mosley | Ceo | Disposed S | 2,900 | $420.77 | $1.22Mn | 365,991 | Direct |
| 01 Apr, 2026 | William D Mosley | Ceo | Disposed S | 2,887 | $421.84 | $1.22Mn | 363,104 | Direct |
| 01 Apr, 2026 | William D Mosley | Ceo | Disposed S | 2,444 | $422.93 | $1.03Mn | 360,660 | Direct |
| 01 Apr, 2026 | William D Mosley | Ceo | Disposed S | 1,469 | $423.98 | $622.82K | 359,191 | Direct |
| 01 Apr, 2026 | William D Mosley | Ceo | Disposed S | 1,500 | $424.92 | $637.38K | 357,691 | Direct |
| 01 Apr, 2026 | William D Mosley | Ceo | Disposed S | 1,000 | $425.94 | $425.94K | 356,691 | Direct |
| 01 Apr, 2026 | William D Mosley | Ceo | Disposed S | 800 | $426.93 | $341.55K | 355,891 | Direct |