X0306 4 2014-11-20 0 0001616707 Wayfair Inc. W 0001103804 VIKING GLOBAL INVESTORS LP 55 RAILROAD AVENUE GREENWICH CT 06830 0 0 1 0 0001621607 Viking Long Fund GP LLC 55 RAILROAD AVENUE GREENWICH CT 06830 0 0 1 0 0001621596 Viking Long Fund Master Ltd. 55 RAILROAD AVENUE GREENWICH CT 06830 0 0 1 0 0001133006 HALVORSEN OLE ANDREAS 55 RAILROAD AVENUE GREENWICH CT 06830 0 0 1 0 0001621842 Ott David C. 55 RAILROAD AVENUE GREENWICH CT 06830 0 0 1 0 0001621691 Purcell Thomas W. JR 55 RAILROAD AVENUE GREENWICH CT 06830 0 0 1 0 0001621588 Sundheim Daniel S. 55 RAILROAD AVENUE GREENWICH CT 06830 0 0 1 0 Class A Common Stock 2014-11-20 4 P 0 17600 22.7292 A 1791536 I See Explanation of Responses Class A Common Stock 2014-11-20 4 P 0 17600 22.7292 A 538711 D O. Andreas Halvorsen, David C. Ott, Thomas W. Purcell, Jr. and Daniel S. Sundheim are Executive Committee members of certain management entities including Viking Global Investors LP ("VGI"), Viking Global Performance LLC ("VGP") and Viking Long Fund GP LLC ("VLFGP"). VGI provides managerial services to various investment funds including Viking Global Equities LP ("VGE"), Viking Global Equities II LP ("VGE II") and VGE III Portfolio Ltd. ("VGE III"). VGP is the general partner of VGE and VGE II and the investment manager of VGE III. VLFGP serves as the investment manager of Viking Long Fund Master Ltd. ("VLFM", together with VGE, VGE II and VGE III, the "Viking Funds"; and VLFM together with Mr. Halvorsen, Mr. Ott, Mr. Purcell, Mr. Sundheim, VLFGP and VGI, the "Reporting Persons"). VGI provides managerial services to (i) VGE, which directly holds 99,621 shares of Class A common stock and 327,594 shares of Class B common stock; (ii) VGE II, which directly holds 5,840 shares of Class A common stock and 19,214 shares of Class B common stock; (iii) VGE III, which directly holds 186,679 shares of Class A common stock and 613,877 shares of Class B common stock; and (iv) VLFM, which directly holds 228,410 shares of Class A common stock and 310,301 shares of Class B common stock. Because of the relationships between VGI and the Viking Funds, VGI may be deemed to beneficially own the shares of Class A common stock and Class B common stock directly held by the Viking Funds. VLFGP serves as the investment manager of VLFM. Because of the relationship between VLFGP and VLFM, VLFGP may be deemed to beneficially own the shares of Class A common stock and Class B common stock directly held by VLFM. The Reporting Persons disclaim beneficial ownership of these securities except to the extent of their pecuniary interest therein, and the inclusion of these securities in this report shall not be deemed an admission of beneficial ownership of the reported securities for purposes of Section 16 or for any other purpose. On November 20, 2014, VLFM acquired 17,600 shares of Class A common stock. Consequently, VLFM directly holds 228,410 shares of Class A common stock and 310,301 shares of Class B common stock. (6) The Reporting Persons are jointly filing this Form 4 pursuant to Rule 16a-3(j) under the Exchange Act. (7) Each of O. Andreas Halvorsen, David C. Ott, Thomas W. Purcell, Jr. and Daniel S. Sundheim is signing individually and as an Executive Committee Member of Viking Global Partners LLC, on behalf of VIKING GLOBAL INVESTORS LP and as an Executive Committee Member of VIKING LONG FUND GP LLC, on behalf of itself and VIKING LONG FUND MASTER LTD. /s/ O. ANDREAS HALVORSEN (6)(7) 2014-11-24 /s/ DAVID C. OTT (6)(7) 2014-11-24 /s/ THOMAS W. PURCELL, JR. (6)(7) 2014-11-24 /s/ DANIEL S. SUNDHEIM (6)(7) 2014-11-24