Roommates.com, LLC ("Roommates") operated a widely used website designed to match people renting out spare rooms with people looking for a place to live. Before subscribers to Roommates could search listings or post housing opportunities on the website, they had to create profiles by answering a series of questions. Besides requesting basic information such as name, location, and e-mail address, Roommates required each subscriber to disclose his or her sex and sexual orientation, and whether he or she would bring children to a household. Each subscriber was further required to describe his or her roommate preferences with respect to the same three criteria (sex, sexual orientation, and whether children would be brought to the household). Roommates also encouraged subscribers to provide "Additional Comments" describing themselves and their desired roommate in an open-ended essay. After a new subscriber completed the application, Roommates would assemble his or her answers into a profile page. Subscribers to Roommates were entitled to view their own profile pages and those of others, send personal e-mail messages through the site, and receive notices from Roommates regarding available housing opportunities matching their preferences.

The Fair Housing Councils of the San Fernando Valley and San Diego ("Councils") sued Roommates, alleging that its activities violated the federal Fair Housing Act ("FHA"). The FHA prohibits discrimination in the sale or rental of housing on the basis of "race, color, religion, sex, familial status, or national origin." The FHA also bars making, printing, or publishing, or causing to be made, printed, or published, any notice, statement, or advertisement, with respect to the sale or rental of a dwelling that indicates any preference, limitation, or discrimination based on race, color, religion, sex, handicap, familial status, or national origin, or an intention to make any such preference, limitation, or discrimination.

Roommates argued, however, that it was immune from liability under § 230 of the federal Communications Decency Act, which provides that "[n]o provider . of an interactive computer service shall be treated as the publisher or speaker of any information provided by another information content provider." Did § 230 protect Roommates against liability?