SEC ownership of COSTAR GROUP, INC.

Top holders, 13D/G large-stake signals, insider positions, and transaction flow tied to CIK 0001057352.

Comparable stake leader

VANGUARD PORTFOLIO MANAGEMENT LLC

Disclosed value leader

BlackRock, Inc.

Comparable rows

50/50

Latest evidence

23 Jun 2026

Top shareholders Insider holders Latest transactions
Public ticker
CSGP on Nasdaq
Parsed ownership sources
13D/G, 13F, and 3/4/5
Source: Parsed SEC ownership filingsUse: Compare filing families carefully
Largest SEC-reported holder
VANGUARD PORTFOLIO MANAGEMENT LLC
Ranking: Comparable ownership first, then disclosed value
Ownership snapshot CIK-linked ownership evidence from parsed SEC filings. 3 signals
Comparable ownership rows
50 of 50
Meaning: Rows with safely comparable ownership %
Latest 13D/G holder
VANGUARD PORTFOLIO MANAGEMENT LLC
Source: Latest parsed Schedule 13D/G stake
Latest parsed ownership date
23 Jun 2026
Freshness: Most recent filing date in this holder set
Issuer Names, identifiers, and filing context for this profile. 2 identity fields
Issuer CIK
0001057352
Issuer location
Arlington, VA

Ownership snapshot

Top shareholders of COSTAR GROUP, INC. (13F + 13D/G + 3/4/5)

Grouped by holder across the latest SEC ownership disclosures. Start with comparable ownership when available, then verify the linked 13F, 13D/G, or 3/4/5 evidence.

Comparable stake leader
VANGUARD PORTFOLIO MANAGE...
Disclosed value leader
BlackRock, Inc.
Comparable rows
50/50
Latest evidence
23 Jun 2026
13D/G 13F 3/4/5 Lead comparable stake: 9.1% 13D/G row: VANGUARD PORTFOLIO MANAGEMENT LLC Showing 1-8 of 50 holder rows.

Quick read

VANGUARD PORTFOLIO MANAGEMENT LLC leads the comparable SEC ownership view at 9.1%.

50 of 50 rows have a safely comparable ownership percentage. Use this as a filing-backed starting point, then open the detailed table for source links, reporting role, position value, share count, and filing date.

Open SEC evidence Opens VANGUARD PORTFOLIO MANAGEMENT LLC's linked filing trail.
Comparable ownership Top 5
VANGUARD PORTFOLIO MANAGEMENT LLC 9.1%
VANGUARD CAPITAL MANAGEMENT LLC 7.5%
BlackRock, Inc. 7.5%
Louise S. Sams 0.01%
Robert W. Musslewhite 0.01%

Ownership % is shown only when SEC disclosures are safely comparable across share classes.

Detailed SEC evidence table Showing 1-8 of 50 holder rows
Holder Evidence Ownership % Position 12M Net Δ As of
VANGUARD PORTFOLIO MANAGEMENT LLC
13D/G 13F
Vanguard Portfolio Management · Company
13D/G 13F
9.1%
$1,544,700,692
38,292,035 shares
 $0 31 Mar 2026
VANGUARD CAPITAL MANAGEMENT LLC
13D/G 13F
Vanguard Capital Management · Company
13D/G 13F
7.5%
$1,275,308,639
31,613,997 shares
 $0 31 Mar 2026
BlackRock, Inc.
13D/G 13F
Company
13D/G 13F
7.5%
$2,631,535,419
31,820,259 shares
 $0 31 Mar 2025
Louise S. Sams
3/4/5
Director
3/4/5
0.01%
$1,156,588
28,671 shares
 +$48,360 23 Jun 2026
Robert W. Musslewhite
3/4/5
Director
3/4/5
0.01%
$1,070,583
26,539 shares
 — 23 Jun 2026
John W. Hill
3/4/5
Director
3/4/5
0.01%
$1,068,727
26,493 shares
 -$154,530 23 Jun 2026
Angelique G. Brunner
3/4/5
Director
3/4/5
0%
$743,385
18,428 shares
 — 23 Jun 2026
Rachel C. Glaser
3/4/5
Director
3/4/5
0%
$500,982
12,419 shares
 +$44,940 23 Jun 2026
How to read this table

Rows are grouped by holder and ranked first by SEC-reported ownership % when it is safely comparable, then by disclosed holdings value. — indicates unavailable or non-comparable values; "mixed-class rows" means the latest filing spans non-comparable classes.

Forms 3/4/5 flow

Insider trading overview

Net insider flow leans to buying over the last 12 months. Net value: +$935,826.

Buys
$5,994,762
Insiders: 4
Sells
$5,058,936
Insiders: 3
Net
+$935,826
Shares: +93,026
Window
Last 12 months
4 rolling buckets
Buy value Sell value
Shares: 149,150 Shares: 56,124
Window (months) Buy shares Sell shares Buy value Sell value Net value
0-3 71,430 0 $2,514,208 $0 +$2,514,208
3-6 77,720 0 $3,480,554 $0 +$3,480,554
6-9 0 4,091 $0 $281,172 -$281,172
9-12 0 52,033 $0 $4,777,764 -$4,777,764

Reporting owners

Insider holders from Forms 3/4/5

Showing 1-20 of 21 reporting-owner rows connected to COSTAR GROUP, INC.. Open a relationship link for the CIK-to-CIK filing trail.

Rows
21
Largest Forms 3/4/5 holder
Michael R. Klein
Net 12M change
+$935,827
Latest report
01 Jul 2026
Name Relationship Holdings Value Past Year Net Change Change % Valuation Report Date
Michael R. Klein Director $148,608,311 Mixed 10 Dec 2024
Andrew C. Florance President and CEO, Director $61,713,025 +$4,994,863 +8.8% Filing P/S 01 May 2026
Wheeler Scott T. Chief Financial Officer $28,627,417 Mixed 26 Apr 2024
Christopher J. Nassetta Director $22,164,729 Mixed 27 Nov 2024
Frank Simuro Chief Technology Officer $18,652,095 Mixed 15 Mar 2026
Frederick G. Saint President, Marketplaces $12,685,645 -$3,682,400 -22% Filing P/S 01 Mar 2026
Michael J. Glosserman Director $8,530,163 Mixed 30 Oct 2023
Lisa Ruggles Senior VP, Global Operations $7,871,175 Mixed 15 Mar 2026
Gene Boxer General Counsel and Secretary $4,295,835 Mixed 15 Mar 2026
Michael J. Desmarais Chief Human Resources Officer $3,947,625 Mixed 15 Mar 2026
Christian M. Lown Chief Financial Officer $3,671,772 Median 01 Jul 2026
Laura Cox Kaplan Director $1,393,984 Mixed 17 Jul 2024
Louise S. Sams Director $1,156,588 +$48,360 +4.4% Mixed 23 Jun 2026
Robert W. Musslewhite Director $1,070,583 Mixed 23 Jun 2026
John W. Hill Director $1,068,727 -$154,530 -13% Mixed 23 Jun 2026
Cynthia Cammett Cann Chief Accounting Officer $995,873 -$315,406 -24% Mixed 15 Jun 2026
Angelique G. Brunner Director $743,385 Mixed 23 Jun 2026
Rachel C. Glaser Director $500,982 +$44,940 +9.9% Mixed 23 Jun 2026
Christine M. McCarthy Director $467,338 Mixed 23 Jun 2026
John L. Berisford Director $453,219 Mixed 23 Jun 2026

Recent insider transactions for COSTAR GROUP, INC.

Showing up to 300 recent insider transactions from the last 12 months.

Insider Symbol Class Transaction % SEC-reported value SEC-reported price Shares Shares owned Date Ownership
Christian M. Lown CSGP Common Stock, par value $0.01 per share Tax liability -4.14% -5,597 129,653 01 Jul 2026 Direct
Rachel C. Glaser CSGP Common Stock, par value $0.01 per share Award 198.8% 8,262 12,419 23 Jun 2026 Direct
John L. Berisford CSGP Common Stock, par value $0.01 per share Award 277.9% 8,262 11,235 23 Jun 2026 Direct
John W. Hill CSGP Common Stock, par value $0.01 per share Award 45.3% 8,262 26,493 23 Jun 2026 Direct
Angelique G. Brunner CSGP Common Stock, par value $0.01 per share Award 81.3% 8,262 18,428 23 Jun 2026 Direct
Robert W. Musslewhite CSGP Common Stock, par value $0.01 per share Award 45.2% 8,262 26,539 23 Jun 2026 Direct
Louise S. Sams CSGP Common Stock, par value $0.01 per share Award 40.5% 8,262 28,671 23 Jun 2026 Direct
Christine M. McCarthy CSGP Common Stock, par value $0.01 per share Award 248.6% 8,262 11,585 23 Jun 2026 Direct
Cynthia Cammett Cann CSGP Common Stock, par value $0.01 per share Tax liability -1.83% -461 24,687 15 Jun 2026 Direct
Andrew C. Florance CSGP Common Stock, par value $0.01 per share Purchase 4.33% $2,514,208 $35.20 71,430 1,722,865 01 May 2026 Direct
Gene Boxer CSGP Common Stock, par value $0.01 per share Tax liability -0.5% -482 95,463 15 Mar 2026 Direct
Lisa Ruggles CSGP Common Stock, par value $0.01 per share Tax liability -1.67% -2,977 174,915 15 Mar 2026 Direct
Frank Simuro CSGP Common Stock, par value $0.01 per share Tax liability -2.61% -11,107 414,491 15 Mar 2026 Direct
Michael J. Desmarais CSGP Common Stock, par value $0.01 per share Tax liability -3.17% -2,873 87,725 15 Mar 2026 Direct
Cynthia Cammett Cann CSGP Common Stock, par value $0.01 per share Tax liability -4.53% -1,194 25,148 15 Mar 2026 Direct
Cynthia Cammett Cann CSGP Common Stock, par value $0.01 per share Award 19.9% 4,374 26,342 10 Mar 2026 Direct
Andrew C. Florance CSGP Common Stock, par value $0.01 per share Award 8.13% 124,162 1,651,435 10 Mar 2026 Direct
Christian M. Lown CSGP Common Stock, par value $0.01 per share Award 9.98% 12,268 135,250 10 Mar 2026 Direct
Gene Boxer CSGP Common Stock, par value $0.01 per share Award 29.6% 21,920 95,945 10 Mar 2026 Direct
Michael J. Desmarais CSGP Common Stock, par value $0.01 per share Award 24.2% 17,676 90,598 10 Mar 2026 Direct
Louise S. Sams CSGP Common Stock, par value $0.01 per share Purchase 5.15% $48,360 $48.36 1,000 20,409 06 Mar 2026 Direct
Rachel C. Glaser CSGP Common Stock, par value $0.01 per share Purchase 31.7% $44,940 $44.94 1,000 4,157 02 Mar 2026 Direct
Frederick G. Saint CSGP Common Stock, par value $0.01 per share Purchase 7.7% $906,600 $45.33 20,000 279,851 02 Mar 2026 Direct
Christian M. Lown CSGP Common Stock, par value $0.01 per share Tax liability -5.51% -7,175 122,982 01 Mar 2026 Direct
Andrew C. Florance CSGP Common Stock, par value $0.01 per share Tax liability -3.76% -59,593 1,527,273 01 Mar 2026 Direct
Gene Boxer CSGP Common Stock, par value $0.01 per share Tax liability -5.79% -4,547 74,025 01 Mar 2026 Direct
Michael J. Desmarais CSGP Common Stock, par value $0.01 per share Tax liability -8.01% -6,353 72,922 01 Mar 2026 Direct
Cynthia Cammett Cann CSGP Common Stock, par value $0.01 per share Tax liability -5.93% -1,385 21,968 01 Mar 2026 Direct
Lisa Ruggles CSGP Common Stock, par value $0.01 per share Tax liability -4.78% -8,931 177,892 01 Mar 2026 Direct
Frank Simuro CSGP Common Stock, par value $0.01 per share Tax liability -4.21% -18,702 425,598 01 Mar 2026 Direct
Frederick G. Saint CSGP Common Stock, par value $0.01 per share Tax liability -4.1% -11,096 259,851 01 Mar 2026 Direct
Christian M. Lown CSGP Restricted Stock Units Award 39,652 39,652 27 Feb 2026 Direct
Frederick G. Saint CSGP Restricted Stock Units Award 39,652 39,652 27 Feb 2026 Direct
Andrew C. Florance CSGP Restricted Stock Units Award 83,708 83,708 27 Feb 2026 Direct
Gene Boxer CSGP Restricted Stock Units Award 26,888 26,888 27 Feb 2026 Direct
Michael J. Desmarais CSGP Restricted Stock Units Award 17,926 17,926 27 Feb 2026 Direct
Cynthia Cammett Cann CSGP Restricted Stock Units Award 6,834 6,834 27 Feb 2026 Direct
Lisa Ruggles CSGP Restricted Stock Units Award 28,197 28,197 27 Feb 2026 Direct
Frank Simuro CSGP Restricted Stock Units Award 52,869 52,869 27 Feb 2026 Direct
Andrew C. Florance CSGP Common Stock, par value $0.01 per share Purchase 3.64% $2,480,654 $44.52 55,720 1,586,866 27 Feb 2026 Direct
Frank Simuro CSGP Common Stock, par value $0.01 per share Tax liability -0.99% -4,421 444,300 19 Feb 2026 Direct
Frank Simuro CSGP Common Stock, par value $0.01 per share Disposed to Issuer -6.41% -30,727 448,721 19 Feb 2026 Direct
Frederick G. Saint CSGP Common Stock, par value $0.01 per share Tax liability -0.79% -2,149 270,947 19 Feb 2026 Direct
Frederick G. Saint CSGP Common Stock, par value $0.01 per share Disposed to Issuer -6.05% -17,583 273,096 19 Feb 2026 Direct
Andrew C. Florance CSGP Common Stock, par value $0.01 per share Tax liability -1.24% -19,221 1,531,146 19 Feb 2026 Direct
Andrew C. Florance CSGP Common Stock, par value $0.01 per share Disposed to Issuer -6.34% -104,983 1,550,367 19 Feb 2026 Direct
Lisa Ruggles CSGP Common Stock, par value $0.01 per share Tax liability -1.69% -3,219 186,823 19 Feb 2026 Direct
Lisa Ruggles CSGP Common Stock, par value $0.01 per share Disposed to Issuer -8.47% -17,583 190,042 19 Feb 2026 Direct
Frank Simuro CSGP Common Stock, par value $0.01 per share Tax liability -0.86% -4,151 479,448 15 Feb 2026 Direct
Andrew C. Florance CSGP Common Stock, par value $0.01 per share Tax liability -1.05% -17,482 1,655,350 15 Feb 2026 Direct
* marks a reported price that did not pass the local price check.
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