How Did Facebook Gain Its Initial Traction?

quora.com

Adam D'Angelo, early Facebook employee

At Harvard the founders invited their friends and sent emails to some mailing lists. At some other early schools they relied on their friends at those schools to spread it socially or by sending emails to mailing lists.

The key for solving the cold start problem in general, though, especially for schools where there was already a competitor, was cross-school friend connections, which was a feature that wasn't added until there were already a few schools (initially the schools were completely isolated instances of the application). After that point, users at the existing schools could search for and connect with or invite friends at the newly-launched schools.

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