Exhibit 4.3

[FORM OF FACE OF CERTIFICATE]

CG

[LOGO]

COSTAR GROUP, INC.

COMMON STOCK

INCORPORATED UNDER THE LAWS OF THE STATE OF DELAWARE

SEE REVERSE FOR CERTAIN DEFINITIONS

CUSIP 22160N 10 9

This Certifies that

is the owner of

FULLY PAID AND NON-ASSESSABLE SHARES OF THE COMMON STOCK, $.01 PAR VALUE, OF

COSTAR GROUP, INC.

transferable on the books of the Corporation by the holder hereof in person or by duly authorized Attorney upon surrender of this Certificate properly endorsed. This Certificate is not valid until countersigned and registered by the Transfer Agent and Registrar.

Witness the facsimile seal of the Corporation and the facsimile signatures of its duly authorized officers.

Dated:

[SIGNATURE]

GENERAL COUNSEL AND SECRETARY

[SEAL]

[SIGNATURE]

PRESIDENT AND CHIEF EXECUTIVE OFFICER

COUNTERSIGNED AND REGISTERED:

AMERICAN STOCK TRANSFER & TRUST COMPANY, LLC

(Brooklyn, NY)

BY

TRANSFER AGENT AND REGISTRAR

AUTHORIZED SIGNATURE

[FORM OF REVERSE OF CERTIFICATE]

COSTAR GROUP, INC.

The Corporation will furnish without charge to each stockholder who so requests, a statement of the powers, designations, preferences and relative, participating, optional or other special rights of each class of stock or series thereof and the qualifications, limitations or restrictions of such preferences and/or rights.

The following abbreviations, when used in the inscription on the face of this certificate, shall be construed as though they were written out in full according to applicable laws or regulations:

TEN COM – as tenants in common

TEN ENT – as tenants by the entireties

JT TEN – as joint tenants with right of

survivorship and not as tenants

in common

UNIF GIFT MIN ACT– _____________Custodian_____________

(Cust)              (Minor)

under Uniform Gifts to Minors

Act_______________________________

(State)

Additional abbreviations may also be used though not in the above list.

For value received,______________hereby sell, assign and transfer unto

PLEASE INSERT SOCIAL SECURITY OR OTHER

IDENTIFYING NUMBER OF ASSIGNEE

(PLEASE PRINT OR TYPEWRITE NAME AND ADDRESS, INCLUDING ZIP CODE OF ASSIGNEE)

Shares

of the capital stock represented by the within Certificate, and do hereby

irrevocably constitute and appoint

Attorney

to transfer the said stock on the books of the within named Corporation with full

power of substitution in the premises.

Dated

NOTICE:

THE SIGNATURE TO THIS ASSIGNMENT MUST CORRESPOND WITH THE NAME AS WRITTEN UPON THE FACE OF THE CERTIFICATE IN EVERY PARTICULAR, WITHOUT ALTERATION OR ENLARGEMENT OR ANY CHANGE WHATEVER.

SIGNATURE(S) GUARANTEED:

THE SIGNATURE(S) SHOULD BE GUARANTEED BY AN ELIGIBLE GUARANTOR INSTITUTION (BANKS, STOCKBROKERS, SAVINGS AND LOAN ASSOCIATIONS AND CREDIT UNIONS WITH MEMBERSHIP IN AN APPROVED SIGNATURE GUARANTEE MEDALLION PROGRAM), PURSUANT TO S.E.C. RULE 17Ad-15.