Over the past 12 months, Costar insiders bought $8.48 million of stock on the open market (232.45K shares) and sold $534,282 (12.38K shares).
| # | Insider | Position | Direct | Indirect | Total | Share of Insiders | Last Filed |
|---|---|---|---|---|---|---|---|
| 1 | Michael R Klein | Director | 1,848,592 | 0 | 1,848,592 | 32.3% | 11 Dec, 2024 |
| 2 | Andrew C Florance | Founder And Ceo | 1,806,165 | 0 | 1,806,165 | 31.6% | 05 Aug, 2026 |
| 3 | Frank Simuro | Chief Technology Officer | 414,491 | 0 | 414,491 | 7.2% | 17 Mar, 2026 |
| 4 | Scott T Wheeler | Chief Financial Officer | 303,417 | 0 | 303,417 | 5.3% | 30 Apr, 2024 |
| 5 | Frederick G. Saint | President, Marketplaces | 278,415 | 0 | 278,415 | 4.9% | 04 Aug, 2026 |
| 6 | Christopher J Nassetta | Director | 229,715 | 0 | 229,715 | 4.0% | 02 Dec, 2024 |
| 7 | Lisa Ruggles | Senior Vp, Global Operations | 174,915 | 0 | 174,915 | 3.1% | 17 Mar, 2026 |
| 8 | Christian M. Lown | Chief Financial Officer | 129,653 | 0 | 129,653 | 2.3% | 06 Jul, 2026 |
| 9 | Michael J Glosserman | Director | 101,465 | 0 | 101,465 | 1.8% | 01 Nov, 2023 |
| 10 | Gene Boxer | General Counsel And Secretary | 95,463 | 0 | 95,463 | 1.7% | 17 Mar, 2026 |
| 11 | Michael J Desmarais | Chief Human Resources Officer | 87,725 | 0 | 87,725 | 1.5% | 17 Mar, 2026 |
| 12 | Robin Jack Rossmann | Chief Financial Officer | 85,935 | 0 | 85,935 | 1.5% | 16 Oct, 2026 |
| 13 | Louise S Sams | Director | 28,671 | 0 | 28,671 | 0.5% | 24 Jun, 2026 |
| 14 | Robert W Musslewhite | Director | 26,539 | 0 | 26,539 | 0.5% | 24 Jun, 2026 |
| 15 | John W Hill | Director | 22,993 | 0 | 22,993 | 0.4% | 10 Aug, 2026 |
| 16 | Cynthia Cammett Cann | Chief Accounting Officer | 18,822 | 0 | 18,822 | 0.3% | 10 Aug, 2026 |
| 17 | Angelique G. Brunner | Director | 18,428 | 0 | 18,428 | 0.3% | 24 Jun, 2026 |
| 18 | Laura Cox Kaplan | Director | 17,835 | 0 | 17,835 | 0.3% | 05 Aug, 2024 |
| 19 | Rachel C Glaser | Director | 12,419 | 0 | 12,419 | 0.2% | 24 Jun, 2026 |
| 20 | Christine M Mccarthy | Director | 11,585 | 0 | 11,585 | 0.2% | 24 Jun, 2026 |
| 21 | John L Berisford | Director | 11,235 | 0 | 11,235 | 0.2% | 24 Jun, 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 |
|---|---|---|---|---|---|---|---|---|
| 15 Oct, 2026 | Robin Jack Rossmann | Chief Financial Officer | Disposed F | 756 | $32.00 | $24.19K | 85,935 | Direct |
| 07 Aug, 2026 | Cynthia Cammett Cann | Chief Accounting Officer | Disposed S | 4,788 | $30.78 | $147.37K | 18,822 | Direct |
| 05 Aug, 2026 | John W Hill | Director | Disposed S | 3,500 | $30.21 | $105.74K | 22,993 | Direct |
| 04 Aug, 2026 | Andrew C Florance | Founder And Ceo | Acquired P | 83,300 | $29.89 | $2.49Mn | 1,806,165 | Direct |
| 01 Aug, 2026 | Frederick G. Saint | President, Marketplaces | Disposed F | 1,436 | $28.76 | $41.30K | 278,415 | Direct |
| 01 Aug, 2026 | Cynthia Cammett Cann | Chief Accounting Officer | Disposed F | 1,077 | $28.76 | $30.97K | 23,610 | Direct |
| 31 Jul, 2026 | Robin Jack Rossmann | Chief Financial Officer | Acquired A | 34,771 | $0.00 | $0 | 34,771 | Direct |
| 31 Jul, 2026 | Cynthia Cammett Cann | Chief Accounting Officer | Acquired A | 26,078 | $0.00 | $0 | 26,078 | Direct |
| 01 Jul, 2026 | Christian M. Lown | Chief Financial Officer | Disposed F | 5,597 | $29.36 | $164.33K | 129,653 | Direct |
| 23 Jun, 2026 | Rachel C Glaser | Director | Acquired A | 8,262 | $0.00 | $0 | 12,419 | Direct |
| 23 Jun, 2026 | John W Hill | Director | Acquired A | 8,262 | $0.00 | $0 | 26,493 | Direct |
| 23 Jun, 2026 | John L Berisford | Director | Acquired A | 8,262 | $0.00 | $0 | 11,235 | Direct |
| 23 Jun, 2026 | Christine M Mccarthy | Director | Acquired A | 8,262 | $0.00 | $0 | 11,585 | Direct |
| 23 Jun, 2026 | Louise S Sams | Director | Acquired A | 8,262 | $0.00 | $0 | 28,671 | Direct |
| 23 Jun, 2026 | Angelique G. Brunner | Director | Acquired A | 8,262 | $0.00 | $0 | 18,428 | Direct |
| 23 Jun, 2026 | Robert W Musslewhite | Director | Acquired A | 8,262 | $0.00 | $0 | 26,539 | Direct |
| 15 Jun, 2026 | Cynthia Cammett Cann | Chief Accounting Officer | Disposed F | 461 | $32.04 | $14.77K | 24,687 | Direct |
| 01 May, 2026 | Andrew C Florance | President And Ceo | Acquired P | 68,330 | $35.17 | $2.40Mn | 1,719,765 | Direct |
| 01 May, 2026 | Andrew C Florance | President And Ceo | Acquired P | 3,100 | $35.82 | $111.04K | 1,722,865 | Direct |
| 15 Mar, 2026 | Cynthia Cammett Cann | Chief Accounting Officer | Disposed F | 1,194 | $43.63 | $52.09K | 25,148 | Direct |