A product requirements document (PRD) is a written specification of what a product or feature should do, for whom, and why. It is used to align stakeholders before engineering begins and to capture the decisions and tradeoffs that shape a build, typically authored by a product manager in collaboration with design and engineering. It is the single most-debated artifact in modern product management because the right level of detail varies enormously by team size, product complexity, and engineering culture.
The classical PRD template (Microsoft / Marty Cagan era) ran 20 to 40 pages and covered problem statement, user stories, functional requirements, non-functional requirements, success metrics, dependencies, ris...