CofounderFit is a structured assessment and alignment tool designed for two founders who are considering a formal business partnership. The platform uses a series of 62 questions to evaluate compatibility across eight dimensions: leadership style, risk tolerance, communication style, decision making, stress resilience, work-life values, work approach, and strategic orientation. Each founder creates a profile, invites their cofounder, and both must complete the assessment independently before a comparison is generated. The result is a compatibility signal on a 0 to 100 scale for that specific pair, not a pass or fail verdict, but a starting point for explicit conversation. The primary workflow involves four steps: creating a founder profile, inviting the cofounder, surfacing tension areas through the comparison report, and documenting decisions. The tool helps founders turn implicit assumptions about work, risk, communication, and conflict into concrete topics to review. It also provides a methodology for documenting roles, decision rights, equity, and vesting in a founder charter and a pre-agreement that can be shared with a lawyer. The assessment is intended to be used alongside a short trial collaboration to decide which conversations cannot remain implicit. Typical use cases include first-time founders evaluating a potential partnership, established cofounder pairs seeking to formalize their agreements, and accelerators that want to facilitate founder alignment. The platform is distinct from general matching services because it focuses on a single existing relationship rather than suggesting new matches. CofounderFit is accessed via a web browser at cofounderfit.com, and users begin with a free profile before deciding whether to proceed with the full comparison. No technical downloads or specialized hardware are required.