Organization and Business Description	12 Months Ended
Dec. 31, 2019
Accounting Policies [Abstract]
Organization and Business Description	1. Organization and Business Description CarGurus, Inc. (the “Company”), is a global, online automotive marketplace connecting buyers and sellers of new and used cars. Using proprietary technology, search algorithms, and innovative data analytics, the Company provides information and analysis that create a differentiated automotive search experience for consumers. The Company’s marketplace empowers users worldwide with unbiased third-party validation on pricing and dealer reputation, as well as other useful information that aids them in finding “Great Deals from Top-Rated Dealers.” The Company is headquartered in Cambridge, Massachusetts and was incorporated in the State of Delaware on June 26, 2015. The Company operates principally in the United States and has also launched online marketplaces under the CarGurus brand in Canada, the United Kingdom, Germany, Italy, and Spain. The Company has subsidiaries in the United States, Canada, Ireland, and the United Kingdom. In the United Kingdom, the Company also operates the PistonHeads online marketplace as an independent brand. On October 16, 2017, the Company completed its initial public offering (“IPO”), in which the Company issued and sold 3,205,000 shares of its Class A common stock, including the full exercise by the underwriters of their option to purchase 705,000 shares of Class A common stock, at a public offering price of $16.00 per share for aggregate gross proceeds of $51.3 million. The Company received $43.2 million in net proceeds after deducting $3.6 million of underwriting discounts and commissions and $4.5 million in offering costs. In addition to shares of Class A common stock issued and sold by the Company, certain selling stockholders sold an aggregate of 7,605,000 shares of Class A common stock, including the full exercise by the underwriters of their option to purchase 705,000 shares of Class A common stock, as part of the IPO. Upon the closing of the IPO, all of the outstanding shares of convertible preferred stock automatically converted into 20,188,226 shares of Class A common stock and 40,376,452 shares of Class B common stock. The 40,376,452 shares of Class B common stock subsequently converted into 40,376,452 shares of Class A common stock resulting in a total conversion of all outstanding shares of convertible preferred stock into 60,564,678 shares of Class A common stock. Subsequent to the closing of the IPO, there were no shares of convertible preferred stock outstanding. The Company is subject to a number of risks and uncertainties common to companies in its and similar industries and stages of development including, but not limited to, rapid technological changes, competition from substitute products and services from larger companies, management of international activities, protection of proprietary rights, patent litigation, and dependence on key individuals.

Organization and Business Description

12 Months Ended

Dec. 31, 2019

1. Organization and Business Description

CarGurus, Inc. (the “Company”), is a global, online automotive marketplace connecting buyers and sellers of new and used cars. Using proprietary technology, search algorithms, and innovative data analytics, the Company provides information and analysis that create a differentiated automotive search experience for consumers. The Company’s marketplace empowers users worldwide with unbiased third-party validation on pricing and dealer reputation, as well as other useful information that aids them in finding “Great Deals from Top-Rated Dealers.”

The Company is headquartered in Cambridge, Massachusetts and was incorporated in the State of Delaware on June 26, 2015. The Company operates principally in the United States and has also launched online marketplaces under the CarGurus brand in Canada, the United Kingdom, Germany, Italy, and Spain. The Company has subsidiaries in the United States, Canada, Ireland, and the United Kingdom. In the United Kingdom, the Company also operates the PistonHeads online marketplace as an independent brand.

On October 16, 2017, the Company completed its initial public offering (“IPO”), in which the Company issued and sold 3,205,000 shares of its Class A common stock, including the full exercise by the underwriters of their option to purchase 705,000 shares of Class A common stock, at a public offering price of $16.00 per share for aggregate gross proceeds of $51.3 million. The Company received $43.2 million in net proceeds after deducting $3.6 million of underwriting discounts and commissions and $4.5 million in offering costs. In addition to shares of Class A common stock issued and sold by the Company, certain selling stockholders sold an aggregate of 7,605,000 shares of Class A common stock, including the full exercise by the underwriters of their option to purchase 705,000 shares of Class A common stock, as part of the IPO. Upon the closing of the IPO, all of the outstanding shares of convertible preferred stock automatically converted into 20,188,226 shares of Class A common stock and 40,376,452 shares of Class B common stock. The 40,376,452 shares of Class B common stock subsequently converted into 40,376,452 shares of Class A common stock resulting in a total conversion of all outstanding shares of convertible preferred stock into 60,564,678 shares of Class A common stock. Subsequent to the closing of the IPO, there were no shares of convertible preferred stock outstanding.

The Company is subject to a number of risks and uncertainties common to companies in its and similar industries and stages of development including, but not limited to, rapid technological changes, competition from substitute products and services from larger companies, management of international activities, protection of proprietary rights, patent litigation, and dependence on key individuals.