Product Specification
A written description of how a product behaves — feature by feature, scenario by scenario. Distinct from a technical spec, which describes implementation.
A product specification answers the question “what does this product actually do?” without requiring the reader to understand how it's built. It describes behaviour in terms of what a user sees, what they do, and what the product does in response — not classes, functions, or database schemas.
Traditional product specs are written once, before development, and then abandoned. They describe what was planned, not what shipped. A living product specification is different: it's derived from the code, so it reflects what the product actually does right now, and updates on every release.
The audience matters. A product spec is read by product managers, customer success teams, engineering managers, and stakeholders. It isn't read by compilers. That's why the format matters: structured enough to be unambiguous, plain enough that nobody needs a glossary.
Related Terms
Documentation that is structurally incapable of falling out of sync with the product, because it is derived from the code rather than written separately.
A single plain-language description of how a product behaves in a specific situation. The atomic unit of a living product specification.
Further Reading
See it in practice
The Specsight demo shows real scenarios, features, and a complete living product spec — generated from an actual codebase.