CoStar Group Inc
Ownership
Ownership Structure
Who owns CoStar Group Inc (CSGP)? This page shows the largest institutions and funds, the ownership structure and the latest insider transactions. 99.2% of the shares are freely tradable; institutional investors hold 104.1%.
Largest Shareholders
Institutions
| Name | Stake (%) | Shares | Change (%) | Date |
|---|---|---|---|---|
| Vanguard Portfolio Management, LLC | 9.44 | 38,234,133 | +0.0 | 03/31/2026 |
| BlackRock Inc | 8.34 | 33,808,184 | -0.5 | 03/31/2026 |
| Vanguard Capital Management, LLC | 6.77 | 27,423,903 | +0.0 | 03/31/2026 |
| State Street Corp | 4.60 | 18,650,975 | +0.1 | 03/31/2026 |
| Capital Research & Mgmt Co - Division 3 | 4.11 | 16,643,016 | +7.3 | 06/30/2026 |
| BAMCO Inc | 4.03 | 16,314,175 | -16.3 | 03/31/2026 |
| Amvescap Plc. | 3.94 | 15,947,525 | +7.0 | 03/31/2026 |
| Baillie Gifford & Co Limited. | 3.25 | 13,154,165 | -3.4 | 06/30/2026 |
Funds
| Name | Stake (%) | Shares | Change (%) | Date |
|---|---|---|---|---|
| Vanguard Real Estate Index Investor | 3.92 | 15,895,272 | -0.1 | 07/31/2026 |
| Baron Partners Retail | 3.82 | 15,488,217 | +113.6 | 06/30/2026 |
Largest reported positions according to regulatory filings; stake as a percentage of shares outstanding, change versus the previous filing. Source: fundamentals data.
Insider holdings
| Person | Role | Shares | Value | As of | Type |
|---|---|---|---|---|---|
| Florance Andrew C | Founder and CEO | 1,806,165 | 52,920,635 $ | Aug 4, 2026 | direct |
| Saint Frederick G. | President, Marketplaces | 278,415 | 8,157,560 $ | Aug 1, 2026 | direct |
| Hill John W | Director | 22,993 | 673,695 $ | Aug 5, 2026 | direct |
| Cann Cynthia Cammett | Chief Accounting Officer | 18,822 | 551,485 $ | Aug 7, 2026 | direct |
Holdings as of each person's most recent SEC Form 4 filing — excluding options and RSUs, which are not shares yet. Holdings may have changed between two filings.
Insiders
Insider Transactions
| Date | Person | Role | Type | Shares | Price | Value |
|---|---|---|---|---|---|---|
| Aug 7, 2026 | Cann Cynthia Cammett | Chief Accounting Officer | Sell | 4,788 | 30.78 | 147,375 |
| Aug 5, 2026 | Hill John W | Director | Sell | 3,500 | 30.21 | 105,735 |
| Aug 4, 2026 | Florance Andrew C | Founder and CEO | Buy | 83,300 | 29.89 | 2,489,837 |
| Aug 1, 2026 | Saint Frederick G. | President, Marketplaces | Other | 1,436 | 28.76 | 41,299 |
| Aug 1, 2026 | Cann Cynthia Cammett | Chief Accounting Officer | Other | 1,077 | 28.76 | 30,975 |
Reportable transactions by officers and major shareholders from SEC Form 4 filings. "Other" includes things like stock grants and option exercises without a buy/sell character. View all insider transactions →
Data as of: September 17, 2026 · Source: fundamental data & SEC filings (annual and quarterly reports, 10-K/10-Q)
Note: pure fact-based analysis, not investment advice and not a solicitation to buy or sell. All figures without guarantee.