Magnite (MGNI) 8-K Changes in Registrant's Certifying Accountant

Exhibit 16.1

August 23, 2018

Securities and Exchange Commission

100 F Street, N.E.

Washington, DC 20549

Commissioners:

We have read the statements made by The Rubicon Project, Inc. (copy attached), which we understand will be filed with the Securities and Exchange Commission, pursuant to Item 4.01 of Form 8-K of The Rubicon Project, Inc.dated August 17, 2018. We agree with the statements concerning our Firm contained therein.

Very truly yours,

/s/ PricewaterhouseCoopers LLP

Los Angeles, California