CSGP CoStar Group Inc

FORM 4 [ ] Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).         
UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP OF SECURITIES                                                                                   
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Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934 or Section 30(h) of the Investment Company Act of 1940                       

1. Name and Address of Reporting Person * SAINT FREDERICK G.	2. Issuer Name and Ticker or Trading Symbol COSTAR GROUP, INC. [ CSGP ]	5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director                    _____ 10% Owner __X__ Officer (give title below)    _____ Other (specify below) President, Marketplaces
(Last)          (First)          (Middle) C/O COSTAR GROUP, INC., 1331 L STREET NW	3. Date of Earliest Transaction (MM/DD/YYYY) 3/23/2021
(Street) WASHINGTON, DC 20005 (City)        (State)        (Zip)	4. If Amendment, Date Original Filed (MM/DD/YYYY)	6. Individual or Joint/Group Filing (Check Applicable Line) _X _ Form filed by One Reporting Person ___ Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1.Title of Security (Instr. 3)	2. Trans. Date	2A. Deemed Execution Date, if any	3. Trans. Code (Instr. 8)		4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5)			5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4)	6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
			Code	V	Amount	(A) or (D)	Price
Common Stock, par value $0.01 per share	3/23/2021		M		2767	A	$204.91	26924 (1)	D
Common Stock, par value $0.01 per share	3/23/2021		M		5067	A	$342.13	31991 (2)	D
Common Stock, par value $0.01 per share	3/23/2021		S		7834	D	$831.70 (3)	24157 (4)	D

Table II - Derivative Securities Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivate Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Trans. Date	3A. Deemed Execution Date, if any	4. Trans. Code (Instr. 8)		5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5)		6. Date Exercisable and Expiration Date		7. Title and Amount of Securities Underlying Derivative Security (Instr. 3 and 4)		8. Price of Derivative Security (Instr. 5)	9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)	10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
				Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares
Option to Acquire Common Stock	$204.91	3/23/2021		M			2767	(5)	3/1/2027	Common Stock	2767.0	$0	0	D
Option to Acquire Common Stock	$342.13	3/23/2021		M			5067	(6)	2/27/2028	Common Stock	5067.0	$0	0	D

Explanation of Responses:
(1)	Represents all shares of Common Stock owned, consisting of 11,717 shares of Common Stock and 12,761 shares of Common Stock subject to unvested Restricted Stock grants, 1,223 shares of Deferred Stock Units and 1,223 shares of unvested Restricted Stock Units.
(2)	Represents all shares of Common Stock owned, consisting of 16,784 shares of Common Stock and 12,761 shares of Common Stock subject to unvested Restricted Stock grants, 1,223 shares of Deferred Stock Units and 1,223 shares of unvested Restricted Stock Units.
(3)	Average based on sales prices ranging from $828.24 to $836.03.
(4)	Represents all shares of Common Stock owned, consisting of 8,950 shares of Common Stock and 12,761 shares of Common Stock subject to unvested Restricted Stock grants, 1,223 shares of Deferred Stock Units and 1,223 shares of unvested Restricted Stock Units.
(5)	The option vested in three equal installments on March 31, 2018, March 31, 2019 and March 31, 2020.
(6)	The option vested in three equal installments on February 28, 2019, February 29, 2020 and February 28, 2021.

Reporting Owners
Reporting Owner Name / Address	Relationships
	Director	10% Owner	Officer	Other
SAINT FREDERICK G. C/O COSTAR GROUP, INC. 1331 L STREET NW WASHINGTON, DC 20005			President, Marketplaces

Signatures
/s/ Jeannette Koonce, Attorney-in-Fact		3/25/2021
**Signature of Reporting Person		Date