What type of beta was Pinterest's prototype launch in March 2010?

Pinterest’s prototype launched as a closed beta in March 2010.

A closed beta is a limited trial in which access is restricted to invited or selected users rather than being open to everyone. Pinterest’s earliest version was made available to a small group of colleagues and family members, allowing the founders to test the product and refine its core idea before expanding access.

This launch was deliberately modest. Pinterest began as a visual bookmarking service where people could collect images and organize them on themed boards. Limiting the audience helped the team observe how people used those boards, what they pinned, and which parts of the interface needed improvement.

The answer is sometimes confused with “open beta,” which describes a publicly accessible test, or “developer preview,” which is usually aimed at software developers evaluating technical features. Pinterest’s March 2010 prototype was not either of those: it was a private, invitation-limited experiment.