Exhibit 31.2

Certification of Principal Financial Officer

pursuant to

Exchange Act Rules 13a-14(a) and 15d-14(a),

as adopted pursuant to

Section 302 of the Sarbanes-Oxley Act of 2002

I, David Day, certify that:

1. I have reviewed this Amendment No. 1 to the Annual Report of The Rubicon Project, Inc. for the year ended December 31, 2017;

2. Based on my knowledge, this report does not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements made, in light of the circumstances under which such statements were made, not misleading with respect to the period covered by this report;

Signature:	/s/ David Day
	David Day Chief Financial Officer (Principal Financial Officer)

Date: April 30, 2018