Product Requirements Document (PRD)

What Is a Product Requirements Document (PRD)?

A product requirements document (PRD) defines what a product or feature must do and why. It captures the problem being solved, the target users, the goals and success metrics, the requirements and the release criteria, giving designers, engineers and testers a shared, testable description of what to build and how success will be judged.

How a PRD Works

In his widely used guide How To Write a Good PRD (2005), Marty Cagan of Silicon Valley Product Group describes the PRD's purpose as stating the product's purpose, features, functionality and behavior clearly and without ambiguity, because the team uses it to build and test the product. He separates it from two neighbors. The market requirements document describes the opportunity or market need; the PRD describes a product that addresses it. The product strategy and roadmap describe where the product is going over several years; the PRD describes one release along that path.

Formats and templates differ between companies, but most PRDs cover the same ground:

• Problem and context: the user or business problem and the evidence behind it.
• Users: target segments or personas and the goals they are trying to reach.
• Objectives and success metrics: what the release must achieve, in priority order, and how it will be measured.
• Requirements: the functional requirements, often written as user stories with acceptance criteria, ranked by priority.
• Release criteria: the non-functional requirements the release must meet. Cagan lists performance, scalability, reliability, usability, supportability and localizability as typical examples.
• Scope boundaries: an explicit out of scope list.
• Assumptions, dependencies, risks and open questions.

Cagan also recommends mapping each requirement to the objective it supports, so that if someone proposes cutting a requirement, the impact on the release goals is obvious. This is an early form of requirements traceability.

PRDs may be documents, wiki pages or structured records in a product tool. In agile teams they tend to be shorter, living documents that link to backlog items, rather than a large contract written once and handed off.

Why a PRD Matters

The PRD is the single place where the "what" and the "why" of a release meet. It aligns product, design, engineering and stakeholders before costly work begins, gives engineers enough to estimate and plan, and gives testers the conditions to verify. It also becomes a record of what was decided, which matters months later when someone asks why the product behaves the way it does.

A strong PRD is testable: a developer could build from it with few open questions, and every requirement can be checked. Weak PRDs fail in two opposite ways. Some are vague, so the team fills gaps with guesses. Others are long and padded, so nobody reads them and they drift out of date.

The bar is higher when AI coding agents implement the work. An agent may infer behavior where the document is silent, so explicit boundaries and reviewable acceptance criteria matter. For agent-specific guidance, see how to write a PRD an AI coding agent will not misinterpret. For keeping requirements reusable after the first release, see how structured requirements make PRDs queryable and traceable.

PRD Example

The following example is hypothetical.

A project management tool plans saved filters. A condensed PRD might read:

• Problem: team leads rebuild the same filter combinations every day, and support tickets regularly ask for a way to save them.
• Users: team leads managing three or more projects.
• Objective: reduce the time it takes to reach a working view. Success metric: share of weekly active team leads who use a saved filter within 30 days of launch.
• Requirements: must save the current filter with a name; must set one saved filter as the default view; should share a filter with the team.
• Release criteria: a saved filter loads in under one second for views with up to 10,000 tasks.
• Out of scope: filters across workspaces and scheduled email reports.
• Open question: should there be a limit on saved filters per user?

PRD vs. Product Specification

The two terms are often used interchangeably, and Cagan himself treats them as synonyms. Where teams separate them, the PRD defines what to build and why, while a product specification defines exactly how the feature will behave: flows, screens, states, data and error messages. Small teams usually keep both in one document; larger teams often write the PRD first and the spec once design work begins.

PRD, MRD, and Requirements Management

A market requirements document explains the market need, target customers, and commercial context. A PRD translates a selected opportunity into product requirements for a defined scope. An MRD may inform several PRDs; teams do not need separate heavyweight documents when a shared, clear record serves the same purpose.

Requirements management is the wider, ongoing process of eliciting, reviewing, prioritizing, changing, and maintaining requirements. The PRD is one artifact within that process. Updating a document once does not establish ownership of later changes or keep linked stories and tests consistent.

For a material revision, record the reason, affected requirements, decision owner, and expected impact. Keep unresolved questions visible and connect requirements to their evidence and acceptance criteria. These practices make a PRD usable as a living agreement while the broader process manages change throughout delivery and operation.